India’s daily tally of Covid-19 cases has more than doubled, climbing to over 7,584 as of June 10 from 3,500 infections recorded until a month ago. Simultaneously, there has been an increase in the uptake of booster doses of the Covid-19 vaccine.

A booster dose is a third shot of a Covid-19 vaccine. In India, it is also called a precautionary dose and administered nine months after the second dose was given.

On April 10, the Indian government approved booster doses at private centres for those aged 18 years and above. At government centres, free booster shots are limited to senior citizens, health and frontline workers.

The demand for booster doses briefly rose to 10 lakh-15 lakh shots per week in April, only to dip by the end of the month. With daily cases on the rise since mid-May, the demand for booster shots again rose, touching 21.08 lakh doses between May 21-May 28.

“The demand is higher than what we saw in March or April,” said Dr Sachin Desai, state immunisation officer in Maharashtra, where 30%-40% of the daily vaccinations are of precautionary doses.

Government officials ascribe the higher demand to concerns over waning immunity levels. India saw a third wave of Covid-19, fuelled by the Omicron variant, in January-February. Those infected in this period acquired a measure of natural immunity against the virus, in addition to the protection given by vaccines. However, some doctors believe that by now the immunity, both natural and vaccine-induced, may have started to decline.

The surge in Covid-19 cases, particularly since the start of June, has deepened these concerns. As a result, more people appear to be opting for a third dose.

Does this mean you should also get a booster dose? spoke to several doctors and health experts about the utility of taking booster shots and found that the responses are mixed, for now.

Should you take a booster shot?

Several public health experts pointed out that the current wave in Kerala and Maharashtra – both states currently account for over 65% of the country’s fresh cases – is mild, and a booster dose may not prevent mild or moderate symptomatic infection or reinfection.

Dr Jayaprakash Muliyil, member of National Technical Advisory Group on Immunisation, said that though five months have passed since the third wave, immunity provided by natural infection will continue to protect the Indian population. “This is assuming that a large population got infected during the third wave,” he said.

Muliyil, a senior citizen, was infected during the third wave. “I have taken the first two doses. I have not taken a booster,” he said, explaining that once the body is exposed to the viral protein through natural infection, it carries the memory for a long time.

This means the body can mount an immune response at a short notice against future infections even if antibody levels decline. “Antibody levels are not an indicator of whether the body has immunity against the infection or not. It is the T-cells and B-cells,” he said.

T-cells are part of the immune system and help kill cells infected by the virus while B-cells generate an immune response. Both are considered memory cells because they carry the memory of how to generate antibodies once exposed to the infection.

“We should be judicious about pushing for boosters for everyone and anyone,” Muliyil said, adding that the current surge of infections appears to be fuelled by sub-lineages BA.4 and BA.5 of the Omicron variant. “Only if a new variant comes, should we consider a booster,” said Muliyil.

Dr Gagandeep Kang, virologist and professor at Christian Medical College, said a booster at this point is apt for those who were not naturally infected and have already received two doses of the vaccine. “That proportion remains small,” she said. “A large population has been infected by Covid-19 in India.”

According to Kang, younger people do not immediately require booster doses. “In senior citizens, three shots may suffice,” she said.

Several doctors, however, advocate boosters for every adult as a precautionary measure. Among them is Dr Balkrishna Adsul, who heads Seven Hills Hospital, a dedicated Covid-19 government facility in Mumbai where 150 patients are currently admitted.

Adsul said there is no harm in paying for a booster shot at a private facility since vaccine prices have been reduced to under Rs 400 per dose. “In our hospital, 60% of patients are vaccinated with two doses and about 6% with a booster shot,” he said. “A booster reduces risk of hospitalisation.”

Dr Rajesh Dere, dean of the Bandra Kurla Complex jumbo centre in Mumbai, said a booster might provide some protection against possible new variants in the near future. “Why wait for a new variant and then rush to take a booster?” he said.

A vaccination centre in New Delhi on April 10. Photo: Money Sharma/AFP

Dr NK Arora, chairperson of the working group of the National Technical Advisory Group on Immunisation, said a booster provides an additional layer of protection for the most vulnerable.

“While hybrid immunity, induced by vaccination and natural infection, works the best, booster dose is useful for those with comorbidities,” he said.

Arora pointed out that 30% of Indians have diabetes, hypertension, heart disease, kidney or liver problems, cancer or other serious comorbidities. “Some do not even know they have diabetes and hypertension,” he said. “In that scenario it is advisable that every adult takes a booster dose.”

On the government’s decision to limit free booster doses to the elderly and frontline workers, Arora said the Union Health Ministry will take a call on expanding free third doses to all adults, not the National Technical Advisory Group on Immunisation. “We can only give technical guidance,” he said.

So far, Delhi, Haryana, and Bihar have made booster shots free for all adults. Assam has expanded free booster coverage to those employed with banks, e-commerce, media, legal firms, transport, communication, energy and the pharmaceutical sector.

Across India, 3.7 crore have taken a precautionary dose. Senior citizens account for a major share – at two crore doses – followed by frontline workers at nearly 90 lakh. Up till June 9, those aged between 18-59 accounted for 30 lakh booster doses.

What are your options for a booster dose?

At the moment, India does not have many options for a booster dose. The country follows a policy of homologous boosters where those who got Covaxin or Covishield as their primary vaccination will get the same vaccine as a booster.

The National Technical Advisory Group on Immunisation has data on heterologous boosters – a combination of different vaccines for a primary and booster doses – but according to chairperson Arora, the technical committee is yet to hold a discussion on the matter.

The Christian Medical College, Vellore, has presented the data of a study involving 200 participants where those who received two doses of Covaxin were given Covishield as a booster and vice versa. The study found a stronger immune response in those given Covishield as a booster after two doses either of Covaxin or Covishield.

A member from the study said the data has been presented to the National Technical Advisory Group on Immunisation twice.

On June 5, the Drug Controller General of India approved Corbevax, a protein subunit vaccine, as the country’s first heterologous booster dose for those aged 18 years and above. It can be administered six months after the second dose. But the vaccine is yet to be rolled out as a booster.

Either the National Technical Advisory Group on Immunisation can approve and recommend Corbevax to the health ministry, or the ministry can include the vaccine in the immunisation programme against Covid-19, which would make it available at private and government centres.

Muliyil said the National Technical Advisory Group on Immunisation is in no hurry to approve Corbevax as a booster. “There is no sense of urgency to include more vaccines,” he said.

According to Muliyil, the health ministry could approve Corbevax without waiting for the recommendation of the National Technical Advisory Group on Immunisation. So far, Corbevax has been approved for use in 12-14 year olds.

Its manufacturer Biological E has supplied 100 million doses to the Centre. Of the total doses, 53.7 million have been used to vaccinate those aged between 12-14 years. If the vaccine is approved as a booster, there will be 46 million doses in stock for use.

Epidemiologist and public health expert Dr Harinder S Ratti said that for the younger population, there is no harm in taking a booster dose.

“But we must understand that the current vaccine is developed for the original strain and the strains have mutated,” he said. “So a booster will not prevent infection.”

Ratti added that he would recommend a booster for those in the high-risk category. “For them it could be life saving.”