Covid-19 vaccination FAQs: Your questions about coronavirus vaccine safety answered

Will both doses of the vaccine ensure I don’t get coronavirus? Are people getting infected after the vaccine? Experts weigh in.

UPDATED: March 28, 2021 6:12 PM IST

With the third phase of Covid vaccination beginning from April 1 in India, myths and misinformation regarding the vaccine continue to stand in the way. When deciding whether to get the vaccine, it’s important to separate myths from facts.

From April 1, people above the age of 45 will not require a comorbidity certificate to get vaccinated. So far, all people above the age of 60 and those above 45 with comorbidities were being vaccinated, apart from medical professionals and frontline workers.

There have been several reports of people across the country getting the infection after the first dose of the vaccine. Some have contracted the disease even after the second dose. Not only this, a lot of people are shunning the mask and throwing caution to the wind after getting vaccinated.

We bust the myths and underscore the facts with India’s top medical experts, Dr Rajeev Jayadevan, Vice Chairman Research Cell IMA Kerala state, and Dr Srinath Reddy, President, Public Health Foundation of India.

From April 1, people above the age of 45 will not require a comorbidity certificate to get vaccinated
From April 1, people above the age of 45 will not require a comorbidity certificate to get vaccinated

1. People are dying/getting infected after the first shot. Should I be worried?

Professor Srinath Reddy: The purpose of the vaccine is to prevent clinically severe disease and death. The immunity conferred by two doses of the vaccine mostly succeeds in preventing severe Covid-19 disease or death from that condition. After the first dose of the vaccine, called the priming dose, immunity starts developing by two weeks, but it is not strong enough. It is only two weeks after the second dose, called the booster dose, that we will see a strong immune response that can counter the virus or death. A mild infection may still occur in a few persons.

The present generation of systemic vaccines, which are administered by intramuscular injection, evoke systemic immunity once the virus has entered the body. They may not prevent infection per se. Mucosal vaccines, which produce secretory antibodies (IgA) in addition to the type of immunity produced by the systemic vaccines, can potentially prevent the initial infection too apart from fighting it. Such sterilising vaccines, which can be taken by inhalation and possibly even orally, are presently still in the early stages of clinical evaluation.

Getting infected or dying from Covid-19, after the first dose, is possible because of these reasons. It does not mean the vaccine is a failure. It emphasises the need to take two doses of the vaccine while protecting oneself against infection through masks, hand washing, physical distancing, and avoiding crowds.

Dr Rajeev Jayadevan: Immunity after a vaccine fully develops two weeks after the second dose. Therefore, people could get sick before that is achieved. That being said, the first dose also confers a degree of immunity, which has been estimated at approximately 70% at three weeks in the case of Covishield. There is no data available in this regard for Covaxin.

2. I have got both doses. Does it mean I won’t get Covid-19?

Professor Srinath Reddy: No. You may still get infected, but it will manifest as a mild disease or even remain asymptomatic. The risk of severe disease and death will be greatly reduced, even if you are infected.

Dr Rajeev Jayadevan: Even after full vaccination is taken, mild infections could occur and that is why people are advised to continue pandemic precautions.

The commonly reported efficacy numbers of 70 to 90% etc refer to the ability of the vaccine to prevent symptomatic infections.

3. Do I need to wear a mask now that I have got a vaccine?

Professor Srinath Reddy: Yes. As long as the virus is circulating freely, the virus can still infect you (even with mild or no symptoms), if you don’t wear a mask. If that happens, there will be some risk that you can transmit the virus to others for a few days, even if you don’t get very sick yourself. So, you must wear a mask to prevent infection to yourself and transmission to others. Only when there is clear and consistent evidence that the virus is no longer in circulation that we can start moving around without masks.

Dr Rajeev Jayadevan: Even after full vaccination is taken, mild infections could occur; and that is why people are advised to continue pandemic precautions.

Remember that even if vaccinated persons pick up a mild infection, they could act as spreaders among the vulnerable. As of March 27, the vast majority of adults in India are unvaccinated and without natural immunity against Covid-19, which means that they are vulnerable.

4. How long will it take for immunity to kick in?

Professor Srinath Reddy: Immunity develops over several weeks. Early antibody response (IgM) is evident in the second week and fades by the fourth week after infection or vaccination. Later antibody response (IgG) starts after two weeks and peaks in a month. Cell-mediated immunity, very important for defence but usually not measured, starts late too but usually lasts even after IgG antibody levels fall in a few months. So, it is best to wait for two weeks after the second dose to feel safe.

Dr Rajeev Jayadevan: Immunity against Covid-19 is multipronged and therefore cannot be reliably measured by checking antibody levels in a lab. T cells are expected to play a major role against severe disease. Vaccines also generate memory cells which could potentially protect for several years.

5. Which vaccines in India are effective against the variants?

Professor Srinath Reddy: As of now, evidence is still accumulating, even as the virus itself is evolving to create new variants. Both vaccines available in India appear to be effective against the variants noted in Britain. Their efficacy against the variant from South Africa is uncertain, as conflicting reports have come on the Astra-Zeneca vaccine which appears to have the property of ‘vaccine escape’ more than any other variant.

So, there will be some uncertainty about Covishield with respect to this variant. Most of the mutations of concern are those in the spike protein, which the virus uses as a key to unlock the entry into human cells. Many of the current vaccines target only the spike protein of the virus. However, an inactivated virus presents more than one antigen to the immune system. It builds a more broadband immunity against several antigens of the virus. So, an inactivated virus vaccine-like Covaxin may be less affected by mutations in the spike protein, compared to vaccines which are directed only against the spike protein. As of now, both available vaccines appear to be effective against the presently circulating mutant forms. We need to keep a close watch as more mutants emerge.

Dr Rajeev Jayadevan: Variants are basically viruses that have significantly different genetic makeup from the original virus. The concern here is that the vaccines were manufactured against the original virus, almost like a key has been made for a particular lock.

Now if the lock has undergone some changes, the same key might not work.

Scientists have been studying this in laboratory conditions and have shown that the variant from South Africa can significantly evade antibodies that were generated both by natural infection as well as through vaccines. However, it must be remembered that a laboratory finding neutralising ability of Serum need not be replicated in terms of efficacy in field conditions.

While this data is noteworthy, what is more important is to follow up those who have been vaccinated and see how they did against variants, compared against the unvaccinated.

The reason why many scientists believe that vaccines will still protect against severe disease from variants is that the T cell epitopes (the part of the virus that is marked for attack by our T cells) are not significantly changed in spite of these mutations.

This means that even with the arrival of variants, the original T cells that were generated by the original infection or the original vaccine could still protect against severe disease.

There is published evidence that Covaxin is effective against the variant from Britain called B.1.1.7 in lab studies, and the whole virus inactivated vaccines similar to Covaxin are similarly effective in lab studies against the variant from South Africa. There is also published evidence that the Astra-Zeneca Covishield vaccine is effective against B.1.1.7 in lab studies.

6. How many in India need to be vaccinated for herd immunity to be developed?

Professor Srinath Reddy: There is no clear evidence, as yet, as to what the herd immunity threshold (HIT) for this vaccine is. Estimates have varied from 60-80% of the susceptible individuals in a population. Since this is a new virus, we are treating all persons as susceptible. Some scientists have challenged that and said that some persons may not be susceptible due to non-specific immunity conferred by other infections or other factors and proposed that HIT can be 40-50%. In contrast to that, we have recently seen evidence of a raging epidemic in the Brazilian city of Maunas despite 76% of the population testing positive for antibodies against the virus.

Herd immunity is a concept applicable to a population, not to each individual in that population. Assuming a HIT of 70%, a population that has attained that level still has 30% susceptible individuals. As long as the circulation of the virus is blocked by the bodies of the 70% who are immune, this 30% is safe. However, if they move out of that ‘herd’ (population), to another where the immunity levels are at 25-30%, they no longer have a protective cordon to block the virus. This 30% do not have a magic cloak of herd immunity to carry everywhere. As non-immune individuals, they are now vulnerable. In a world, where travel is frequent within and between countries, susceptibility will remain a threat till all countries have crossed the HIT. That will only happen with large-scale immunisation supplementing infection acquired immunity. Even Indians who travel only within the country must realise that herd immunity is not transferable from location to location.

Dr Rajeev Jayadevan: Immunity against Covid-19 is multipronged and therefore cannot be reliably measured by checking antibody levels in a lab. T cells are expected to play a major role against severe disease. Vaccines also generate memory cells which could potentially protect for several years.

7. When will children get the vaccine?

Professor Srinath Reddy: Most of the earlier vaccine trials started for people who are at least 18 years of age and did not include children. Some trials later extended to 12 years. Recently, makers of the Pfizer-BioNTech vaccine have announced that trials will be carried out in children, under 12 years from as young as 6 months. We have to await evidence of safety and efficacy from each of these trials before any recommendations can be made for vaccinating children.

Dr Rajeev Jayadevan: Children have a remarkably low death rate of 1:50,000, compared to 7,500 per 50,000 among those above 85 who get Covid-19. They get diseases like Multisystem Inflammatory Syndrome in children (MIS-C), which are severe inflammatory conditions as a result of the infection.

The prime concern in India is whether they will act as spreaders. Schools act as hubs for the virus, connecting multiple homes in a geographical region. Infection from one household can easily reach many others through this hub, where children spend hours together.

Indian schools tend to be crowded; their dynamics are different compared to western nations. Therefore, data from schools in the west won’t apply here.

India has multigenerational households, where children could bring the virus home from school. Even if the child does not get sick, older relatives, such as grandparents could suffer severe consequences when schools open.

It is not known whether the present-day vaccines will reduce the asymptomatic spread of disease among children. Trials are ongoing. Once the results of these trials are available, we will be in a better position to decide on vaccination among children.

Vaccines that specifically enhance mucosal immunity will also play a role in the future.



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