Component of Vaccine Development Essay

Complete an ANNOTATED bibliography in APA format (12 pt. Times New Roman, double-spaced, 1-inch margins).

• Address the following assignment requirements as it relates to disaster management – disease outbreak preparedness, response and recovery efforts Component of Vaccine Development Essay

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o Summarize and evaluate a minimum of 10 (ten) peer-reviewed journal articles published within the past 5 years that address current research topics in public health.

o Each annotation must be a minimum of 250 words and include the following:

▪ Summary of the resource content

▪ Evaluation of resource utility

▪ Assessment of resource credibility and reliability

o Paraphrase information to demonstrate your own understanding of the topic in the context of public health research.

The Coalition for Epidemic Preparedness Innovations (CEPI) was created as a result of an emerging global consensus
that a coordinated, international, and intergovernmental effort was needed to develop and deploy new vaccines to
prevent future epidemics. Although some disease outbreaks can be relatively brief, early outbreak response activities
can provide important opportunities to make progress on vaccine development. CEPI has identified six such areas
and is prepared to work with other organisations in the global community to combat WHO priority pathogens,
including the hypothetical Disease X, by supporting early activities in these areas, even when vaccine candidates are
not yet available.
Introduction
Over the past two decades, a succession of infectious
disease outbreaks and epidemics have challenged the
emergency preparedness and response systems of global
public health institutions. The 2014–15 Ebola epidemic in
parts of west Africa and the 2015–16 Zika virus epidemic
in Central America and South America were key events
that galvanised global efforts to strengthen global health
security.
Examples of the global efforts to prepare for infectious
disease outbreaks include the Global Health Security
Agenda (GHSA), a partnership of more than 64 countries
and international organisations that was established in
February, 2014, to strengthen the ability of countries to
prevent, detect, and respond to epidemics; the World
Bank’s Pandemic Emergency Financing Facility (PEF),1
which was launched in May, 2016, can rapidly make
funds available for epidemic response; and the WHO
Research and Development (R&D) Blueprint,2
endorsed  Component of Vaccine Development Essay
in May, 2016, by the World Health Assembly, to increase
the speed of medical product development to quell
outbreaks. Learning from the lengthy process needed to
develop vaccines against epidemic diseases, such as
Ebola virus and Zika virus, the Coalition for Epidemic
Preparedness Innovations (CEPI), was launched at the
Davos Summit in January, 2017, with a mandate to speed
the development of vaccines against epidemic diseases.
The global need for CEPI became apparent in the
wake of the 2014–15 Ebola epidemic, which exposed
deep inadequacies in the responses of the institutions
responsible for safeguarding the public against the
wide-ranging negative consequences of infectious
disease outbreaks.3
The Ebola epidemic killed more than
11 000 people and cost the economies of Guinea, Liberia,
and Sierra Leone, some of the worst affected countries, a
cumulative US$53 billion.4 Despite the public and
private sector’s successful development and deployment
of an experimental vaccine towards the end of the
epidemic, the collective response to Ebola virus disease
fell short, and a better system to produce effective
vaccines against epidemic threats was needed.
CEPI was launched as a response to the emerging
consensus that a coordinated, international, and
intergovernmental effort was required to develop and
deploy new vaccines to prevent future epidemics. As such,
CEPI’s mission is to stimulate, finance, and coordinate
vaccine development against diseases with epidemic
potential when market incentives are unsuccessful.
CEPI has prioritised investments in two areas. The first
is the development of vaccines against a set of highpriority pathogens, initially the Lassa virus, Middle East
respiratory syndrome coronavirus (MERS-CoV), and
Nipah virus, and, more recently, Rift Valley fever virus
and the chikungunya virus. The second is the development
of vaccine platform technologies that will enable rapid
vaccine development and manufacturing. CEPI’s focus
on the high-priority pathogens was informed by WHO’s
R&D Blueprint for action to prevent epidemics and based
on a number of other factors, including the risk of an
outbreak occurring, transmissibility of the pathogen,
burden of disease, and feasibility of vaccine development.2
CEPI’s investments in vaccine platform technologies aim
to expedite vaccine development to improve global
capacity to respond to the emergence of an unknown
pathogen with epidemic potential (referred to as Disease X
in the WHO R&D Blueprint).
CEPI set an initial funding goal of $1 billion, on the
basis of an analysis of what it would cost to fund the
development of four to six candidate vaccines for two to
three diseases on the WHO Blueprint list through to
phase 2, and to develop an investigational stockpile of
those vaccines.5
To date, CEPI has secured commitments
and aligned investments of more than $750 million
toward that goal, which includes investments from
Norway, Germany, Japan, the Bill & Melinda Gates
Foundation, the Wellcome Trust, and the European
Commission, in addition to investments from Australia,
Belgium, Canada, and the UK.
Initiatives like CEPI, GHSA, PEF, and WHO R&D
Blueprint are mutually reinforcing; for example, the PEF
has released funds to support the response to the
2018–2019 outbreak of Ebola virus disease in the
Democratic Republic of the Congo.6 Component of Vaccine Development Essay
Under the rubric of
the WHO R&D Blueprint, WHO will publish diseasespecific roadmaps, describing key knowledge gaps
relevant to the prevention, diagnosis, and treatment of
Lancet Infect Dis 2019;
19: e399–403
Published Online
June 27, 2019
http://dx.doi.org/10.1016/
S1473-3099(19)30305-6
Coalition for Epidemic
Preparedness Innovation, Oslo,
Norway (R Hatchett MD,
Prof N Lurie MD)
Correspondence to:
Dr Richard Hatchett, Coalition for
Epidemic Preparedness
Innovation, London NW1 2BE, UK
[email protected]
For more on CEPI see http://
www.cepi.net
For more on GHSA see

Global Health Security Agenda

e400 www.thelancet.com/infection Vol 19 November 2019
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outbreaks of priority pathogens, including those related
to CEPI’s development efforts.7
These roadmaps highlight
core product-development needs, including animal
models for testing vaccines and biological standards and
assays required for assessment of vaccine candidates,
which must be addressed to successfully develop and test
vaccines. These needs, in turn, are included in CEPI’s
initial vaccine development projects and other crosscutting
initiatives that aim to advance vaccine candidates for
these diseases.
The importance and limitations of
disease-specific roadmaps
The roadmaps are an important articulation of the
knowledge gaps and critical needs that exist for the
development of vaccines, diagnostics, and therapeutics
for priority pathogens. The development of these roadmaps and the information within them, which have not
previously been consolidated into one place, required a
major effort led by WHO and its partners, including the
members of disease-specific task forces and the Center for
Infectious Disease Research and Policy at the University
of Minnesota (Minneapolis, MN, USA) among others.
Although the roadmaps are an important starting
point for epidemic preparedness, they alone cannot
drive progress. Translation of these roadmaps into
action is essential. WHO, with its unparalleled ability to
convene multisector stakeholders and capacity for
global advocacy, will be pivotal to the translation process.
However, WHO does not directly support research and
will have to work through its partners to make progress.
In fact, no single organisation, coordinating authority,
or national government is accountable for ensuring
that the knowledge gaps outlined in the roadmaps are
specifically addressed in a timely manner, especially
during outbreak situations, which provide rare
opportunities to study the priority pathogens. Clear
identification in advance of research activities that can
be undertaken during or immediately after an outbreak
of the epidemic is also an essential part of preparedness.
The global community will need to come together to fill
the gaps identified by the disease-specific roadmaps in
an efficient, organised, and coordinated way. In view of
its mandate to develop vaccines against diseases that
pose an epidemic threat, CEPI is both willing and well
positioned to help fill outbreak-related gaps identified by
the WHO roadmaps as they relate to vaccine development.
Outbreaks as an opportunity for vital research Component of Vaccine Development Essay
CEPI initially envisioned it would support research in an
acute outbreak only once the candidate vaccines it is
supporting were ready for phase 3 clinical trials. However,
it is clear that, while they might often be brief, outbreaks
present important opportunities to collect essential data
that have the potential to accelerate vaccine and other
medical countermeasure development.8 To take full
advantage of these opportunities, closing the gap between
the onset of an outbreak and the execution of research is
critical.
Outbreaks involving the pathogens highlighted in
the WHO R&D Blueprint are sporadic, but they can be
deadly. In 2018 alone, there were outbreaks of six of the
ten priority pathogens.9
Therefore, acting with urgency
to expedite and optimise the vaccine development work
that can be achieved between outbreaks and preparing
for the work that can only be done during outbreaks is
crucial.
CEPI has identified a set of research activities it believes
are needed to accelerate vaccine development, which can
be undertaken during outbreaks and before the availability
of vaccine candidates that are ready for testing in humans.
These activities will hasten vaccine development and
result in earlier vaccine deployment in future outbreaks
and thus should be prioritised in current plans.
We have identified five areas of vaccine-related research
that can be advanced during outbreaks, speeding vaccine
development (table). These proposed areas of research
build on the WHO R&D Blueprint and disease-specific
roadmaps as well as the key components of a research
response to public health emergencies identified by Lurie
and colleagues8 Component of Vaccine Development Essay
and Modjarrad and co-workers.10
Although this list of research areas is not exhaustive, it
represents a focused set of research and data collection
priorities from a vaccine development perspective.
Where invited to do so by competent authorities in the
affected countries, CEPI stands ready to support these
activities as they relate to WHO priority pathogens and
Disease X.
The table describes key activities related to vaccine
development that can be advanced through research
done during outbreaks, along with relevant preparatory
actions that should be completed in advance. Tailoring
the activities to the needs and capabilities of the
countries and investigators involved will be essential.
We believe that these efforts, although challenging, can
be undertaken alongside and in coordination with WHO
and others involved in outbreak-control and outbreakresponse efforts and that with careful planning there can
be important synergies with these activities. CEPI’s
long-term goal is the development of vaccines that could
affect outbreak control in the future.
Key vaccine development actions that should
occur during an outbreak
Sequence, serotype, and share the outbreak strain
Pathogen sequencing has become a normal part of
outbreak response and helps clarify the origin of the
outbreak and its transmission patterns. Serotyping is
important for identifying whether a vaccine candidate is
likely to protect against the circulating strain. Access to
circulating viruses is crucial for the development of
regulatory tools, such as biological standards, assays, and
animal models, which are central to vaccine development,
testing, and licensure. In addition, newer techniques,
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such as deep sequencing, could be helpful if considered
early in the response.
Collect acute and convalescent specimens
Well curated, acute, and convalescent blood (or other
body fluid) specimens are crucial, particularly for poorly
understood pathogens. Characterising the human immune response to infection is essential for identifying
correlates of protection and for developing suitable
animal models for vaccine development; an important
component of this work is the collection of blood from
survivors. Collection of appropriate volumes of antibodyrich serum from survivors are essential for the international standards and assays that are needed for vaccine Component of Vaccine Development Essay

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(and diagnostic test) development, testing, and release,
and for comparing one product (or even vaccine lot) with
another. Similarly, specimen processing to obtain and
analyse peripheral blood mononuclear cells, although
a more labour intensive process, is pivotal for the
isolation and identification of light-chain and heavychain antibody sequences and the development of
recombinant antibodies. Such specimens can also be
used for the development of rapid diagnostic tests,
vaccine design, therapeutics, and for the identification of
correlates of protection, which can be useful as surrogate
endpoints in vaccine trials. Validated measures of
immune response are required before any regulatory
authorisation for vaccine use can be granted. Such measures do not currently exist for Lassa virus, MERS-CoV,
or Nipah virus, CEPI’s initial priority pathogens, nor
will they exist for the hypothetical Disease X. Ideally, the
scientific community should agree on priorities for
specimen analysis in advance of an outbreak, and the
collection and distribution effort should be designed to
serve the needs of vaccine, diagnostics, and therapeutics
developers. However, if a disease outbreak occurs and
consensus on an analysis plan has not been reached,
specimens could be safely processed and stored,
maintaining a chain of custody in a national or regional
biobank until the outbreak has ended and a scientific
consensus on their analysis can be achieved.
Accelerate development of diagnostic tests that can
serve as endpoints for vaccine trials
Diagnostic tests can serve multiple functions, including
surveillance, diagnosis, and the guidance of clinical
decision making. Development of diagnostic tests specifically for vaccine development might not be of the
highest priority during an outbreak response. However,
these tests are required to guide an outbreak response
and are likely to aid the performance of epidemiological
studies, the organisation of vaccine clinical trials, and
the measurement of the immune response. Diagnostictest developers can facilitate vaccine development by
focusing on tests (eg, highly accurate PCR tests and
serological assays) that can simultaneously support
rapid case identification and management while serving
as clinical endpoints for regulatory vaccine trials. Given
the low number of and poor access to health care and
laboratory infrastructure in the countries where some of
the WHO priority pathogens are endemic, newer
techniques that support the development of both point
of care testing and antigen detection that can be used in
vaccine trials (eg, next-generation sequencing and
Actions before an outbreak Actions during an outbreak
Sequence, serotype, and
share outbreak strain
Identify people and agencies, including local investigators, who will be expected to undertake this activity;
ensure that MTAs, safe storage and transport, and fair allocation mechanisms for sharing specimens are in place;
ensure mechanisms are in place for rapid release of funds to support the research  Component of Vaccine Development Essay
Sequence, serotype, and disseminate results;
share outbreak strain with vaccine and animal
model development teams
Collect acute and
convalescent blood
samples and other body
fluid specimens
Identify and fund investigators, including local investigators collaborating with front-line caregivers, who will collect
and process specimens and maintain chain of custody; ensure specimen collection and handling is consistent with
expected analytic needs; ensure that protocols, MTAs, and safe storage and transport (if needed) are in place; seek
preapproval of protocol from ethics committee; ensure funding, supplies, and personnel are ready to begin when
outbreak starts
Collect and transport or safely store
specimens; if not done in advance with WHO,
convene a scientific advisory committee to
prioritise how samples should be interrogated
and who they should be allocated to
Accelerate development
of diagnostic tests that
can serve as endpoints
for vaccine trials
Determine which diagnostic tests will likely be needed to support vaccine development, particularly tests that are
different from those needed for outbreak detection and response; identify possible researchers and organisations
who can develop these tests, and ensure protocols and agreements are in place, and that they have needed access to
funds; collaborate with the specimen collection effort to ensure panels for test validation are rapidly assembled, and
a process for allocating them is in place
Develop and validate diagnostic tests that
will be needed for vaccine development;
if relevant, ensure additional specimens are
available for post outbreak validation and
confirmation
Do epidemiological
studies essential for
vaccine development
Identify and assess current surveillance systems and address key gaps relevant to vaccine development; ensure
investigators who will work alongside outbreak response teams to collect data needed for vaccine development,
trial design, and planning are trained and prepared; to the greatest extent possible, develop collection and testing
protocols with investigators and public health authorities in advance of outbreak, and seek preapproval from the
ethics committees; plan coordination between clinical trial teams and outbreak investigators, if a trial or vaccination
effort is anticipated (eg, ring vaccination); ensure personnel, supplies, and rapidly available funding are in place
Collect and analyse epidemiological data
(eg, seroprevalence, incidence, transmission
dynamics, and geographical distribution)
to support vaccine trial planning
Understand cultures and
beliefs Component of Vaccine Development Essay
Identify behavioral and anthropological science team with relevant linguistic and cultural competencies; develop
generic protocols for understanding knowledge, attitudes, beliefs in community, and seek preapproval of ethics
committees; develop a just-in-time training package for local community members who will be involved in the
work; ensure personnel, supplies, funding, and rapidly available funding are in place
Understand community beliefs regarding the
disease, its control, and vaccination; provide
community education through locally trained
and trusted workforce
MTA=material transfer agreement.
Table: Key vaccine development activities that should occur before and during a disease outbreak
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targeted genome or pathogen capture methods) should
be prioritised.
Implement epidemiological studies essential for vaccine
trial design
Epidemiological studies are not only essential for disease
prevention and control but also for planning and preparing
clinical trials of promising vaccine candidates. Understanding of how to better prevent and control many of
these diseases will only be possible through targeted
epidemiological studies during outbreaks. Establishing the
baseline incidence, seroprevalence, and transmission
dynamics of the target disease, determining the role of
vectors and potential need for animal vaccines, identifying
disease hotspots, elucidating seasonal patterns of exposure,
understanding the full clinical spectrum of illness, and
having a validated widely shared case definition that can
serve as a trial endpoint will facilitate planning for and
increase the efficiency of clinical trials done both in the
interepidemic period and during an outbreak. Given
the sporadic and unpredictable occurrence of outbreaks,
the study designs suitable to different prototypes of
transmission dynamics, and infrastructure must be in
place and tested before an outbreak begins. Even if
vaccines are licensed through alternative pathways, such
as the US Food and Drug Administration’s Animal Efficacy
Rule, post-licensure effectiveness data will need to be
generated during outbreaks. Doing epidemiological
studies in populations at risk before the implementation of
clinical trials will also strengthen local research capacity
and facilitate community engagement, which in turn
might result in better enrolment in vaccine effectiveness
studies.Component of Vaccine Development Essay
Understanding cultures and beliefs
Social and anthropological factors will affect disease
control and, ultimately, serve to guide community mobilisation and facilitate vaccine acceptance. Having a safe and
effective vaccine that is unacceptable to a population who
could benefit from it would represent a failure of vaccine development and outbreak management. Outbreaks
represent a time of both fear and of exceptional focus,
presenting important opportunities for behavioral and
anthropological science team to enhance understanding
of knowledge, attitudes, and beliefs that might shape
participation in clinical trials and vaccine acceptance more
generally.
CEPI’s role in outbreak research
Recent accounts of the challenges facing research during
outbreaks are sobering but motivating, highlighting both
progress and the importance of good preparation, and
operational and diplomatic excellence.11 The WHO
R&D Blueprint, disease-specific roadmaps, and Global
Coordination Mechanism are fulfilling essential roles in
highlighting research gaps related to outbreaks, coordinating aspects of the research response, research funding
during outbreaks, and highlighting the research priorities
of affected countries. Our goal in this paper is to highlight
the research areas that are central to vaccine development
and important subsets of outbreak response activities.
Because planning is central to any disease outbreak
research effort, CEPI has begun to identify and support
preparedness activities that will enable a rapid research
response in areas essential for vaccine development, even
before vaccine candidates are ready for human trials.
Using Lassa fever research as proof of concept for
preparatory research activities that can be done in advance
of clinical trials, CEPI issued calls for proposals aimed
at collecting blood specimens from survivors of Lassa
fever, to allow better characterisation of the immune
response and to accelerate the development of assays and
standards in September 2018.12 Similarly, CEPI will fund
collaborative efforts among research groups to analyse
epidemiological data needed to design and support
vaccine trials.13 Both efforts require research teams in
endemic countries to be preidentified, have protocols that
have been reviewed, at least provisionally, by national
ethics committees, have good working relationships with
their respective ministries of health and frontline
caregivers, and be able to engage with communities.
CEPI is committed to data sharing and transparency.
The coalition is a signatory to the WHO statement
of Public Disclosure of Clinical Trial Results14 and is
committed to publish its data in open access journals.
CEPI expects the research teams it supports to uphold
these commitments. If these Lassa virus-related efforts
are successful, CEPI will support related efforts for
MERS-CoV and Nipah virus.Component of Vaccine Development Essay
CEPI has set aside funds for vaccine development
during outbreaks and, pending vaccine availability at the
time of an outbreak, the coalition stands ready to support
the research response areas described previously for the
priority pathogens and for unknown pathogens against
which vaccine development is contemplated. The knowledge generated through this research is crucial for vaccine
development and planning for clinical trials. The activities
outlined in the table should be viewed as necessary to
initiate or accelerate vaccine development but they might
also be useful in clarifying whether, and how far, vaccine
development should proceed. Given the magnitude of
investment needed to develop a new vaccine and take it to
licensure, CEPI anticipates that its early funding of these
types of activities will be essential for rapid decisionmaking processes involving a wide range of global
stakeholders. CEPI will work closely with affected
countries and the WHO Emergencies Programme to
coordinate and support this potentially catalytic work.
CEPI is both a freestanding organisation and a coalition, and its mandate to speed the development of
vaccines means that in the event of an outbreak of a new
disease, or if such provisions are not in place when an
outbreak begins, CEPI will work with affected countries
and global partners through the Global Coordination
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Mechanism to support the conduct of such critical work
as quickly as feasible. CEPI will continue to work with
the international community on plans to implement
vaccine trials during an outbreak once its vaccine
candidates reach an appropriate stage of development,
and to establish investigational vaccine stockpiles. Ultimately, development of a response to outbreak research
will be pivotal to the success of CEPI’s mission to
advance vaccines against epidemic diseases.Component of Vaccine Development Essay

A vaccine is a collection of immunological determinants which are presented to the immune system as killed or live antigens which provoke protective immune responses. The development of vaccines against viral and bacterial diseases is one of the greatest achievements of human endeavours. Vaccination is the most cost effective and efficient way to control viral diseases. The use of conventional viral vaccines has saved humans and animals from dreaded disease epidermics.

Infectious diseases which account for about 30-50% deaths due to lack of effective chemotherapeutic agents and that do exists are often too costly. Thus vaccines have become important tools for fighting infectious diseases in many parts of the world. On the other hand, in developed countries these infectious diseases account only 4-8% of all deaths. This low incidence of infectious diseases is largely due to the wide spread use of vaccination. The well-known example is eradication of smallpox with the help of smallpox vaccine.

Similarly use of several other vaccines like diphtheria, poliomyelitis, measles and rubella resulted dramatic decrease of diseases incidence and mortality. Further vaccination is much inexpensive than treating people who are already sick with modern antibiotics and other chemotherapeutic agents. Some of the commonly used vaccines are listed in Table 19.1.Component of Vaccine Development Essay

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Vaccines continue to play an important role in veterinary medicine. However, sometimes these traditional vaccines become serious problem. Recombinant DNA techniques and synthetic organic chemistry have had major impact in overcoming, some of these problems and developing vaccines of a new type. Apart from this, some modern molecular approaches (Table 19.2) are applied. These methods enabled us to develop vaccines against diseases for which traditional vaccines do not exist.

Development of Vaccines:
Some of the noval approaches currently in the process of development of vaccines are:

1. Synthetic vaccines,

2. Recombinant subunit vaccine,

3. Genetically altered live vaccines,

4. Vectored vaccines,

5. DNA vaccines, and

6. Plant and plant viruses based vaccines.

7. Vaccines against bacteria, and

8. Future.

1. Synthetic Vaccines:

Two decades long research have revealed that small synthetic peptide having sequences of immunogenic epitopes on a protein will react with antibody to the intact native antigen and in some cases neutralize the biological activity. Anderer and Schlumberger (1965) demonstrated that chemically synthesized peptides corresponding to protein fragment would also produce the virus neutralizing antibody.Component of Vaccine Development Essay

This observation led to an extensive research on synthetic antigens. Sale et al. (1992) demonstrated that a synthetic fragment of 20 amino acids corresponding to 89-108 of the coat protein of MS2 (a bacteriophage) elicited antibodies which reacted with the intact virus particle. These initial observations provided a ground for the subsequent exploration of peptide immunogen.

The identification of genes encoding immunogenic proteins and availability of nucleic acid sequences allowed derivation of amino acid sequence of the immunogenic peptides.

There are several advantages of synthetic peptide vaccines:

(i) They possess indefinite shelf life,

(ii) Would have precise composition,

(iii) No possibility for the adventitious presence of live virus, and

(iv) Costly handling facilities are not necessary. A number of different diseases have been the target for synthetic vaccines e.g. FMDV, influenza and Hepatitis B.Component of Vaccine Development Essay

Though significant protective immune responses have been achieved in experimental conditions, the synthetic vaccines are far from the commercialization mainly due to poor immunogenicity, short-term immunity and high cost of vaccination. Now the focus is on improving the immunogenicity by incorporating B and T lymphocyte epitopes and better adjuvants in the synthetic peptides.

2. Recombinant Subunit Vaccines:

The understanding that isolated proteins of viruses can provoke protective immune response, led to application of genetic engineering in cloning, expression of critical viral genes in prokaryotic and eukaryotic expression vectors. Thus, the immunogenic peptides of the viral origins could be expressed in bacteria and yeasts. The concept of a subunit vaccine contain only those immunogenic components that are necessary to elicit a protective response and excluding unnecessary that has several alternative features.

Subunit vaccines lack infectivity and hence no complication of arising out of vaccination in immunocompromised individuals. Subunit vaccination eliminates allogenic immunosuppressive and other undesirable reactogenicity. These vaccines also exhibit a great deal of stability.Component of Vaccine Development Essay

The first successful recombinant vaccine was produced against hepatitis B. This has paved the way for the development of other recombinant peptide vaccines. The other recombinant vaccine which is in advanced stage of development is against parvovirus B19. Though the recombinant subunit vaccines are quite safe, there are still considerable problems like poor immunogenicity, high cost of production, short term immunity etc. Until these problems are tackled effectively, it is unlikely that the recombinant subunit vaccines will hit the market in near future.

3. Genetically Altered Live Vaccines:

Conventionally attenuated or naturally found avirulent strains of viruses have been used to develop live vaccines. Now with the development of rDNA technology, it is possible to attenuate a virus by deleting or altering the virulent genes. This kind of gene manipulation reduces its virulence or makes it unable to replicate completely and thus make a live vaccine with precisely defined modifications.Component of Vaccine Development Essay

A live Simian Immunodeficiency Virus (SIV) vaccine, attenuated by deleting net gene exhibited the most impressive protection against SIV in macaques. Investigations are in progress to generate live attenuated vaccines for the use in human including improved polio and dengue vaccines. Recently Pirkin et al. (1997) demonstrated the feasibility of using genetically modified live vaccine against influenza-A. Genetically altered live vaccines could be used veterinary vaccines but human factors are to be considered. The clinical trials of such products in human have not been carried out.

4. Vectored Vaccines:

Vectored vaccines approach allows expression of heterogenous genes into an avirulent viral/ bacterial organism which are harmless to vaccinated animals and induce cellular and humoral immune response against the foreign product. This approach also enables expression of more than one foreign genes encoding immunogenic proteins, thus paving the way for development of multivalent recombinant vaccines against human and animal viral infection. In the past one decade, a wide range of viruses and bacteria have been used for expression of relevant foreign genes. The most extensively used vector has been vaccinia virus.

Vectored vaccines against viral diseases are generally based on infectious, semi infected viral, bacterial vectors into which the genes of interest have been cloned. Vaccinia virus has been used as a vector for development of vaccine against rabies and rinderpest. A number of relevant genes of other viruses have been expressed in a variety of vectors and their vaccine potential has been studied extensively.Component of Vaccine Development Essay

5. DNA Vaccines:

Relatively recent approaches in vaccine development are based on the observation that when plasmid containing suitable promoters and the genes encoding immunogenic proteins are injected into tissues, the gene may be expressed and generate humoral and cellular immune responses. The same response can be generated by inoculating relevant nucleic acid into the skin or mucosa.

This approach has generated a great deal of commercial interest due to several advantages including duration of immunity generated and stability of the vaccine. DNA vaccine technology provides exciting new approach for prevention and control of variety of viral diseases.

Delivery of DNA vaccines requires expression of immunogenic proteins in tissues accessible immuno system such as muscle or skin or mucous membranes. For effective transfection and expression of the gene within these tissues, it is imperative that the introduced DNA is supercoiled and it includes strong tissue specific promoter and the transcribed mRNA has poly. A tail to ensure its stability in the host cell. Like plasmid DNA, naked mRNA encoding immunogenic protein can also be directly inoculated into host to induce immune response against the protein product.Component of Vaccine Development Essay

Though the nucleic acid vaccine approach appears very attractive, there are a number of constrains including the possibility of integration of the nucleic acid, persistence and immunotolerance, which can be addressed.

6. Plant and Plant Viruses Based Vaccines:

The results of recent studies have suggested that genetically engineered plants and plant viruses could be used as vaccines. In recent years, several attempts have been made to produce various antigens and antibodies in plants. Antigens and antibodies expressed in plants can be administered orally as any edible part of the plant, or by parenteral route after isolation and purification from the plant tissue.

The edible part of the plant to be used as a vaccine is fed raw to experimental animals or humans to prevent possible denaturation during cooking and avoid cumbersome purification protocols. Thus, plants like tomato, banana and cucumbers are generally, the plants of choice. Virus based vectors can also be used to express the gene transiently to develop the products in a short period.

Plant system has the capability of producing any vaccine in large amounts and in a less expensive manner. However, the purification of the product may require the use of existing or even more cumbersome procedures. Attention, therefore, has been paid to mainly those antigens that stimulate mucosal immune system to produce secretory IgA (S-IgA) at mucosal surface, such as gut and respiratory epithelia.Component of Vaccine Development Essay

Thus, an antigen produced in the edible part of plant can serve as a vaccine against several infectious agents which invade epithelial membranes. The first report of the production of edible vaccine (a surface protein from Streptococcus) in tobacco appeared in 1990 in the form of patent application. Subsequently, a number of attempts were made to express various antigens in plants.

One of the utilities of producing antigens in plants in large amounts is in treatment of autoimmune diseases like diabetes mellitus which involve production of antibodies against glutamic acid dehydrogenase (GAD) and insulin, leading to destruction of insulin producing pancreatic cells. The antigens targeted for autoimmune response can be fed to the animals to induce immune tolerance.

7. Vaccines against Bacteria:

Due to readily availability of wide range of antibiotics against bacterial diseases, not much effort is put on the development of vaccines against these diseases.Component of Vaccine Development Essay

Need of such vaccines being felt due to following reasons:

(1) Not all bacterial diseases are readily treated with antibiotics

(2) The use of antibiotics has resulted in purification of bacterial strains that are resistant to several antibiotics.

(3) Refrigeration facilities for the storage of such antibiotics are not available in many tropical countries.

(4) It is often difficult to ensure that individuals receiving antibiotic therapy have to undergo the full course of treatment. Component of Vaccine Development Essay