The central government has allowed a booster Covid vaccine dose, officially known as a precautionary dose, for everyone above 18 years of age.
With this announcement, I immediately calculated my due date which, as per the current rule, will be nine months from the date of the second dose of the primary vaccine.
But why “nine” months?
The responses of more than half a dozen experts I spoke to – including scientists, government officials, members of NTAGI and doctors – clarified one thing: that there is no scientific basis behind fixing the gap of nine months between the second dose and the booster shot.
For some experts, a nine-month gap is “good enough” because there are scores of individuals who have not received their second doses of a Covid vaccine. Hence, this interval would ensure the availability of vaccines for those individuals as well.
Others believe that India needs to generate more data on both of its vaccines – Serum Institute of India’s Covishield and Bharat Biotech’s Covaxin – to make an informed decision.
Top scientist Anurag Agrawal, former director at the Institute of Genomics and Integrative Biology, told me that he doesn’t think there is sufficient data to know what is an ideal gap. And instead of nine months, the gap can be reduced to six months.
“Especially for the population above 40,” he said, and quickly added that “ideally we need to generate the necessary data to make this more evidence-based than opinion-based”.
Why the nine-month gap doesn’t make sense
It’s no secret that more than 85% of the Indian population has received AstraZeneca-Serum Institute of India (SII) manufactured Covishield.
The Indian manufacturer, SII, and the published studies both vouch for a shorter dose spacing.
Sample this: a study published in The Lancet in December 2021, found waning vaccine protection of ChAdOx1 nCoV-19 (known as Covishield in India) against Covid hospital admissions and deaths in both Scotland and Brazil – this becoming evident within three months of the second dose.
It suggested that “consideration needs to be given to providing booster vaccine doses for people who have received AstraZeneca’s ChAdOx1 nCoV-19”.
According to the WHO, a booster dose of Covishield may be considered 4-6 months after completion of the primary vaccination series. The recommendation was focussed on the higher-priority-use groups.
Recently, SII has also informed the government that the third dose should be administered within six months and the studies in various other countries show that it gives very good results to control the infection.
Data, the WHO and manufacturer are on one side. Then, on what basis is the central government advising a nine-month gap?
Dr Krishna Ella, managing director of Bharat Biotech, maker of Covaxin, also pitched for a six-month gap for a third dose in November 2021.
However, the vaccine is made in collaboration with the central government’s health research wing, the Indian Council of Medical Research (ICMR). Hence, he added a disclaimer that the “final decision was up to the government”.
India’s longest dose spacing
The benefits of booster vaccination have been recognised after increasing evidence of waning vaccine effectiveness against mild and asymptomatic Covid-19 infection over time.
Globally, the gap between booster and primary vaccine regimen varies between two and six months.
For Sinovac’s CoronaVac – which is known as the world’s most widely used vaccine – the gap is between four and six months.
In the United States, booster shots of Pfizer can be taken five months after the second dose.
Those who took Johnson & Johnson’s primary vaccine can get the booster after two months.
Several other countries such as France, Taiwan, Singapore, Australia and Italy have decreased their booster gap to five months.
Finland has recommended a two to four-month booster timeline for at-risk groups and people aged above 60 years.
Sweden has also cut the recommended time interval between the second and third vaccine shot to five months from six.
Japan has squeezed the gap for booster shots for those aged 64 and below to seven months from the earlier mandate of eight months. And for those aged 65 and above, the gap is six months after the second dose.
Reduce the gap, at least to six months
With a hint of a slight surge in Covid-19 cases in some states, the government must look at the available evidence at the global level, if there is a dearth of local data.
Going by a rough calculation, on the basis of a nine-month interval, around 7.03 crore people are eligible to take the booster shots.
The pool of eligible people, with a nine-month gap, is quite low, as India faced difficulties in expanding the coverage of the second dose. The uptake of the second dose remained slow and, hence, only 7.03 crore people got it till July.
If India reduces the interval to six months, those who got the second dose by October 9 will become eligible. It means the pool will expand to include more than 25 crore people who can take boosters or the third dose immediately.
It means the more people covered by the boosters, the more the chances of passing by the upcoming waves without a significant spike in hospitalisations and deaths.
With the balance of more than 20 crore unutilised stock of vaccines with the states and union territories, meeting the demand for boosters may not be a difficult task.
Also, Biological E’s Corbevax can be introduced in the vaccination programme for adults as well. The company has already stockpiled 30 crore doses for the central government and has the capability to manufacture 100 crore doses annually. Similarly, SII’s Covovax can also be added to the inoculation plan.
The government must reduce the gap from nine months to at least six months in the interest of the public at large.
The Centre may possibly make a move soon, a highly placed government official told me as I questioned him over the logic of the nine-month gap. “The decision will depend on the status of Covid cases in India. If cases start surging, the announcement will be rushed. The gap can be reduced to six months instead of nine,” said the official.
The sooner, the better.
WHO’s experts insist that the novel coronavirus is evolving in an unpredictable way and Covid-19 is still a global emergency. India must not forget the scramble for more doses when the country’s vaccination programme was facing a desperate supply shortage amid the rampaging second wave. Today, India is in a comfortable position to expand the booster drive.
The shortened interval will help in controlling an unpredictable and fast spread of various new strains of Covid-19, hence protecting the lives and livelihoods (economy) of Indians.
If science is still figuring out the answers to an ideal dose spacing, let’s choose to err on the side of caution.
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