A health officer in Gujarat and two health officers in Maharashtra were diagnosed with COVID-19 after receiving both the doses of the COVID-19 vaccine thus raising questions on the necessity of the vaccine as well as the efficiency of the same.
BOOM spoke to two scientists who explained how getting infected even after receiving the vaccine is a part of vaccine science and not unusual. Even though people may get infected by the virus, the vaccine leads the body to generate an immune response which may be feeble but also stop the virus from severely affecting the person's body.
Dr. Vineeta Bal, immunologist, IISER Pune said, "all the COVID-19 vaccines approved so far are not transmission blocking vaccines but they do prevent the further proliferation of the virus in the body."
"But if I do get infected after vaccination, the body will have an immune response but it is not necessary that it will stop me from being infected. It may not be severe for me but I could still infect any vulnerable person in my vicinity. Transmit infection yes, disease mostly not. So all of the infected ones could be asymptomatic."
Dr. Sankaran Krishnswamy, biologist, IMS, Chennai corroborated with Dr. Bal. "Vaccination reduces chances of severity and mortality, but not infection completely. To understand whether transmission is affected, a substantial proportion of the population needs to be vaccinated. "
Vaccines as a science are meant to first control the spread of a particular disease, and eventually as a larger proportion of the population is vaccinated, help in building herd immunity and later eliminate the disease. Even the other vaccines such as the polio vaccine, the MMR vaccine are administered to create immunity and protect individuals from contracting the disease. However, in some cases, children still contract the infections and later the diseases but are not necessarily severely affected.
In the clinical trials for the COVID-19 vaccines, it was found that performing PCR testing for presence of SARS-CoV-2 was conducted 14 days after the second shot was administered.
For instance, in the Oxford- AstraZeneca vaccine, participants were seen to develop symptoms of COVID-19 within a 14- day window after receiving both the shots of the vaccine. The time duration between administering the two shots is also considered to be an important parameter for determining efficacy. While preliminary findings suggested that a period of 14 days (2 weeks) would be enough to elicit an immune response, continued research found that a gap of 4-8 weeks between the two shots generates a better and stronger immunogenic response.
As all the COVID-19 vaccines currently approved across the world are in emergency use authorization, research on improving their immunogenicity and efficacy is an ongoing process.
The World Health Organisation, has time and again announced that a vaccine which is even 50-70% effective, will help in controlling the spread of the virus. That means if even 70 out of the 100 vaccinated, do not get infected, but 30 people do, the vaccines will help in reducing the speed of the spread of the virus. Pfizer, Moderna, and the Sputnik virus are over 90% effective. Both the vaccines approved in India, Covishield and Covaxin are 62-71% and 81% effective respectively.
It is also pertinent to remember that the new variants of SARS-CoV-2 that have emerged in the past several months will be identified as a new strain, even by a vaccinated person. The effectiveness of most approved vaccines is now being tested against the English, South African, and Brazilian variants.
With the new strains, the relative newness of COVID-19, and emerging research, there is still some time till the world would have seen the last of COVID-19.
