In Perspective: The booster dose conundrum for India
Last week, the United States (US) became the latest country to allow booster doses of Covid-19 vaccines to be given to at least some people. People above the age of 65, anyone above the age of 18 with co-morbid conditions that raise their susceptibility to severe disease ,and people who work in high-risk environments (health workers) in US are now eligible for a booster, similar to the conditions in most other countries.
Altogether, till September 24, at least 32 countries have now authorised booster doses in some form, according to a Reuters compilation.
The list has gradually grown, despite strong calls against widening booster doses by the World Health Organization, which warned that “administration of booster doses will exacerbate inequities” at a time when “priority populations in some countries, or subnational settings, have not yet received a primary vaccination series”.
The evidence, it said in an interim statement on August 10, “remains limited and inconclusive on any widespread need for booster doses”.
The argument against booster doses
In a September 13 analysis of the available evidence, a group of scientists go into further detail why widespread roll-out of booster doses may be premature at this point. Here is a summary of their conclusions.
Global coverage is key: Unvaccinated people drive most of the transmission and vaccines would do most good in these populations. Reaching them will hasten the end to the pandemic by limiting the variants that can arise in underserved geographies.
Efficacy against severe disease is holding up: Available scientific evidence has “consistently” shown that vaccine efficacy is substantially higher against severe disease, even if they do seem to have fallen significantly in the case of symptomatic disease due to the Delta variant.
Better to wait and watch: If a variant emerges that will hamper efficacy to a great degree, it might be worthwhile to boost using a vaccine designed to take on that variant. Premature boosting can unnecessarily expose people to side effects.
Hesitancy risks may rise: If the need for boosters is not justified by robust data and analysis, the exercise could hamper the confidence in vaccines.
The arguments for booster doses
Among the most significant real-world data on this issue comes from Public Health England, which released its findings as preprint (yet to be peer reviewed) paper on September 15. Largely, it reflects both the WHO’s position and the analysis published in The Lancet. But there are some noteworthy findings, summarised below.
The drop in symptomatic disease in the above-65 age bracket is high: In the case of Vaxzevria (the Oxford-AstraZeneca vaccine), it fell from 63.8% on the first week after the second dose to just 36.66 after 20 weeks.
Efficacy against hospitalisations drops for 65+: Protection from hospitalisation in people above 65 dropped by a near 10 percentage points (in case of Vaxzevria), while for those in 40-64 years age, the reduction was a mere 2.3 percentage point.
Those with immune risks significantly affected: The drop was perhaps most stark in people with illnesses or treatments that suppress their immunity. For instance, even in 40-64 age group, the drop in protection from hospitalisation was over 30 percentage point 20 weeks later.
The challenge for India
The evidence does support that people in higher age groups and those with suppressed immunity should be offered a booster dose. But for a country where less than a quarter of the eligible population has been fully vaccinated, this will not be an easy choice.
The options are complicated by another factor that could be at play in India: infection-induced immunity. Over the past week, the number of new cases was the lowest in six months. It was six months ago that the second wave set in and, according to the latest serosurvey figures by ICMR, two in three Indians have been exposed to the virus.
Population immunity estimates, while dangerous as an input for policy adjustments, can help buy some time.
The receding numbers even when cities have almost entirely opened suggest there may be some protection for now.
Taken together with the low per capita coverage of initial vaccination, it is crucial for India to focus on the unvaccinated and partially vaccinated first. But, as supplies are projected to outstrip demand, the government must take a quick decision.
Over the next month, evidence supports the need for India to at least offer boosters to people in the oldest of age groups, and those battling illnesses such as cancer.
In Perspective takes a deep dive into current issues, the visible and invisible factors at play, and their implications for our future
The views expressed are personal