Is the strategy to administer repeated booster COVID-19 vaccine doses an ultimate solution to fight the virus? No...it is not the right approach, said Dr Chandrakant Lahariya, a leading public health and policy expert in India.
Dr Lahariya said there is some benefit of the third shot over the first two shots, but there's a broad consensus that the fourth and fifth shot has a low additional advantage. "Ideally, at max, one booster shot is needed of the appropriately-selected vaccines," he said.
However, he emphasised that we need to remember that the booster is more useful in a setting where the natural infection has been low. "But in a country like India where there is natural infection and hybrid immunity, there's no such urgency of the booster."
Scientists define hybrid immunity as the immune protection acquired by an individual after getting jabbed with one or more doses of a COVID-19 vaccine and having experienced at least one SARS-CoV-2 infection.
Dr. Mayank Amin draws a Pfizer-BioNTech coronavirus disease (COVID-19) children's booster vaccine. (Reuters)When asked why other countries like the United Kingdom (UK), the United States (US) and Sweden have approved more than one booster shot, he said, "That's their personal decision depending upon the local context. That is not the right approach to do in my opinion."
Dr Lahariya agreed "that the level of antibodies declines (with time)" and "that by giving a booster, the level of antibodies increases." He, however, said, "We don't know what amount of antibodies protect you."
Explaining why repeated booster doses are no solution, Dr Lahariya said, "The boosters are being given with assumptions that higher the antibodies, better the protection. But that may not be the case. With time, the amount of antibodies decline...but we don't know to what extent the level of protection declines."
When asked if there are any benefits of administering a person with more than one booster, he said, "We don't have any information on it and it may vary from one vaccine to other."
He went on to explain the scientific concept of 'original antigenic sin' to highlight the possible drawback of boosting immunity at regular intervals.
"Essentially, when you start boosting your immune system on a repeated interval, then there will be a standard point of time when it will stop responding or it will not get a sufficient response to a future booster...We don't know what will happen, but it is a possibility," the doctor said.
Keeping this in view, he said one should use vaccine boosters more rationally rather than indiscriminately.
"It is up to the experts and scientific individual that how they want to utilise (vaccines)...It's an informed choice that one needs to make, knowing that repeated booster is not a very good option," Dr Lahariya said.
While Dr Lahariya opined against administering repeated boosters, Polly Roy, professor and Chair of Virology at the London School of Hygiene and Tropical Medicine, was in favour of boosters.
A 5-year-old receives a Pfizer-BioNTech coronavirus disease (COVID-19) booster vaccine. (Reuters)"After six months, your immunity level decreases and then you need a booster to improve your immunity against Covid-19...," Professor Polly said.
So does this mean one needs to take boosters for a lifetime? "One doesn't know, the next year this virus might not be there and then there will not be a need to take the COVID-19 booster doses," Professor Polly said.
Boosters are primarily given to individuals who either have a weakened immune system or whose immune response has weakened over time or those who are at the risk of getting a severe infection.
"This extra dose is intended to improve immunocompromised people’s response to their initial vaccine series," a report by Johns Hopkins says.
Like Dr Lahariya and Professor Polly, many scientists and researchers across the world are debating over the vaccination strategy of repeated boosters. Several studies have been conducted to gauge the efficacy of third or fourth booster shots.
Let's take a look at what some studies have found:
A study conducted in the UK and published in The Lancet journal in May 2022 suggested that fourth dose mRNA booster vaccines for COVID-19 are well-tolerated in people jabbed with Pfizer vaccine as the third dose.
"Fourth-dose COVID-19 mRNA booster vaccines are well tolerated and boost cellular and humoral immunity. Peak responses after the fourth dose were similar to and possibly better than, peak responses after the third dose," the study said.
A medical health worker holds up an empty syringe after applies a booster dose of the AstraZeneca coronavirus disease (COVID-19) vaccine (Reuters)Preliminary data analysis of another research published in the New England Journal of Medicine said, "A fourth dose of the BNT162b2 vaccine was effective in reducing the short-term risk of Covid-19–related outcomes among persons who had received the third dose at least 4 months earlier."
The data for this study was recorded by the largest health care organisation in Israel from January 3 to February 18, 2022. The study was conducted on participants aged over 60 years.
A press release by Israel's Ministry of Health said, "...the fourth dose raises protection against severe illness by up to three times and higher compared to those previously-vaccinated with the third dose."
However, 'boosters don’t block infections for long'
Several reports claimed that the immunity from a third vaccine shot is likely to wane within months — hinting that "protection from boosters might be short-lived".
Kanta Subbarao, a virologist at the Peter Doherty Institute for Infection and Immunity in Australia, was quoted by a report as saying, "Because protection from boosters might be short-lived, rolling out endless doses — potentially at the expense of immunising unvaccinated people in low-income nations — is not a viable or reasonable."
A report in Nature journal cited data collected in Israel between June and November last year — when the Delta variant of COVID-19 was dominant — to support the statement.
It said the data "indicated that the immunity from a third (mRNA booster) shot wanes within months, mirroring the decline after two doses".
Meanwhile, the recent study from Israel said, "Despite evidence supporting the effectiveness of a third vaccine dose, including effectiveness against the Omicron variant, a growing body of evidence documents subsequent waning over time of the immune protection from the third dose."
The report also cited real-world data from the United Kingdom, collected in late 2021, suggesting that immunity from boosters might decrease even faster against Omicron than against Delta.
A sign shows the requirements to enter restaurants and bars as the spread of the coronavirus disease (Covid-19) continues in Frankfurt, Germany. (Reuters)Earlier in January 2022, the World Health Organization (WHO) said, “A vaccination strategy based on repeated booster doses of the original vaccine composition is unlikely to be appropriate or sustainable”.
In another release on May 17, the WHO listed seven studies on booster doses. It said, "Taken together, these studies show some short-term benefit of an additional booster dose of mRNA vaccine in health workers, those over 60 years of age or with immunocompromising conditions."
"Data to support an additional dose for healthy younger populations are limited; preliminary data suggest that in younger people, the benefit is minimal," it said.
(Edited by : Akriti Anand)
First Published: Jun 9, 2022 6:58 PM IST
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