Is a Vaccine the Only Answer to the COVID-19 Pandemic?
Are vaccines effective enough, or will we have to find other ways to come to terms with the coronavirus?
There are now 21,751 articles published on Pubmed (which allows search and retrieval of peer-reviewed biomedical and life sciences literature) of which 1024 are related to vaccination.
A search for COVID-19 on Google shows 5.8 billion results of which 32 million pertaining to vaccination. There are now 159 candidate vaccines and several trials are underway across the globe. There is a lot of hope on vaccination helping contain the pandemic.
Vaccination is one of the most cost-effective strategies for the prevention of infectious diseases. However, the mere presence of a very safe and effective vaccine may not be able to protect the community unless it is well-deployed.
There are many such instances where safe and effective vaccines are available, but outbreaks of the disease occur frequently even in most developed countries of the world. Measles outbreak in various countries is an example. After the successful invention of the first vaccine (smallpox) in the world by Sir Edward Jenner, it took 150 years to eradicate the disease.
Since the declaration of the COVID-19 pandemic by WHO, there has been a race for the development of a safe and effective vaccine against the SARS-COVID-2 virus.
As per the latest WHO figures, more than 118 institutions, research and academic bodies including vaccine manufacturers are working at extra speed to develop a vaccine.
While it would be desirable to have a vaccine at the earliest, under normal circumstances, it takes 5-10 years to go through different clinical stages of development of any new vaccine.
However, in epidemic and pandemic situations, many of the stages can be overlapped and regulatory authorities respond very promptly at each stage to accord approval. It is, therefore, expected that in the extraordinary circumstances that we find ourselves in today, in 12-18 months a vaccine should find its way to the market for human use.
We do need to realize that by the time the vaccine is available, perhaps the brunt of the pandemic would have diminished and a substantial proportion of the population would have developed herd immunity by either subclinical or clinical infection.
The world is witnessing a variety of vaccines against COVID-19 produced by different biotechnological methods e.g Inactivated, Vector based, RNA, DNA, Subunit depending upon the expertise and research experience of individual institutions and laboratories.
It may happen that simultaneously 8 vaccines which are in relatively advanced stages of development become available for use. Fifteen vaccines are already in clinical trials.
The vaccines that have received the most publicity are the Oxford and Moderna vaccines. The Oxford university (Jenner laboratory) ChAdOX1 COVID-19 vaccine has been developed using a non-replicating vector-based technology in which a weak Chimp Adenovirus has been identified and the Spike protein RNA of SARS Cov2 is introduced to develop the vaccine.
Stage II/III randomized control trial in humans has already started and the results are expected by the end of September.
The two Moderna vaccine in collaboration with the National Institute of Allergy and Infectious Disease USA is a messenger RNA based vaccine using a two-dose schedule and a phase II clinical trial is progressing.
Two major global vaccine producers, GSK, and Sanofi are collaborating to develop a vaccine. Also, six more vaccines in the USA, Europe, and China are in advanced stages of trials. There are three vaccine manufacturing companies in India that are in the process of producing a COVID-19 vaccine.
Bharat Biotech has three COVID-19 projects. The first one is in collaboration with Thomas Jefferson University where the platform would be a vero cell rabies vaccine in which Spike protein RNA shall be introduced. The second project is in collaboration with the Indian Council of Medical Research (National Institute of virology, Pune) to develop an inactivated vaccine. The third project is with an American company manufacturing Flu vaccine (Flugen) to make a live intranasal vaccine though the same platform.
All three projects are in the initial preclinical stages. Zydus Cadila is in in the early clinical stage of development of aDNA based vaccine as well as a replicating viral vector vaccine. Panacea Biotec is partnering with Refana Inc in the USA to develop a vaccine. Serum Institute of India, Biological E, Bharat Biotech, Indian Immunologicals, and Mynvax is developing vaccines.
Serum Institute of India, the largest vaccine manufacturing company in the world in collaboration with Oxford University will be manufacturing the ChAdOX1 COVID-19 vaccine. BharatBiotech and Biological E have capabilities to manufacture vaccines in very large volumes. There are other indigenous vaccines in various stages of development.
One should remember that no vaccine can provide 100% protective efficacy and any vaccine having more than 80% of efficacy is considered to be a very good vaccine.
The efficacy of a vaccine is judged in human trials and through the production of protective antibodies in significant titre.
In the case of COVID-19, it is the neutralizing antibody. However, the presence of protective antibodies might not translate into the effectiveness of the vaccine.
The effectiveness of the vaccine is determined by its capability to protect against the disease in a community for which several factors play an important role. There are many other factors like cold chain maintenance, ethnicity, age, the response in high-risk individuals and immune-compromised persons, etc. that can influence the success of vaccination.
With less than 80% coverage of any vaccine does not prevent community spread. Unless effectiveness data are available, no one can be certain about how well a new vaccine will perform.
There also needs to be an effective surveillance system for adverse events following mass usage to demonstrate the safety of the vaccine. There has been so much hype about COVID-19 vaccines that many countries have already prebooked millions of doses of vaccine from manufacturers even before the final product is effective
Several challenges need to be addressed before we finally adopt any new vaccine:
- Is the vaccine able to prevent infection or only the serious form of the disease?
- If it prevents only serious disease, then the vaccine shall be helpful in individual protection from a severe form of the disease and not for stopping the pandemic?
- It is still not clear whether one or two doses will be needed?
- Will there be a need for any booster doses?
- What will be the duration of the immunity of the vaccine?
- How will the equitable distribution of the vaccine be ensured?
By the time a safe and effective vaccine becomes available the pandemic may be over and the vaccine may lie unused in significant measure.
Considering the facts that have been discussed, even if an ideal vaccine becomes available, it may not be the panacea for stopping the pandemic. Following general hygienic measures including hand washing, wearing masks, cough and sneeze etiquette and social distancing remain the best tools that are readily available to each one of us to combat COVID-19.
(Dr. Ashok Datta is a Senior Emeritus Pediatrician, Appolo Hospitals Delhi, Dr. Anupam Sibal is a Group Medical Director & Senior Consultant, Paediatric, Gastroenterology, and Hepatology in Appolo Hospitals.)
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