The world is warming up to the idea of booster doses for Covid-19 vaccines, but India is still holding out.

These doses have been recommended in various countries, including the United States and Israel. They were rolled out despite a global shortage of vaccines, with countries in Asia and Africa struggling to administer even the first shot among citizens.

With supply gradually increasing and data indicating vaccines’ waning immunity, vulnerable populations may stand to benefit from a fresh infusion of antibody-producing sera.

India, in fact, should have considered booster shots “yesterday”, according to Dr Swapneil Parikh, Mumbai-based physician and author of The Coronavirus Book. “There is a very urgent need for immunocompromised individuals to receive an additional dose, irrespective of which vaccine they took,” he said.

Those with conditions such as diabetes, cancer and AIDS are not only at a greater risk of contracting Covid-19, medication also suppresses their body’s immune response. In most cases, the bodies of such patients produce fewer disease-fighting antibodies than those of healthier persons.

The elderly, too, face similar risks. Besides, this group is most susceptible to severe Covid-19 and death. The World Health Organization recommends booster shots on priority for this category of people.

What WHO says

The WHO’s Strategic Advisory Group of Experts, on October 11, recommended “additional doses” in the primary series for immunocompromised groups.

Technically, additional doses, which are basically an extension of the primary vaccine series, differ from booster doses.

For instance, if a person took two doses of Covishield, the India-made brand of the AstraZeneca vaccine, a third dose after a short duration will be considered an additional dose.

“In particular, immunocompromised individuals often fail to mount a protective immune response after a standard primary series, but also older adults may respond poorly to a standard primary series,” the WHO notes.

In India, more than 70% of the eligible population have received the first dose so far. Photo credit: Sam Panthaky/AFP

On the other hand, a booster, by the WHO’s definition, is administered when, over time, a person’s immunity “has fallen below a rate deemed sufficient in that population” even after having received the primary vaccination.

For ease of understanding, however, the term “booster dose” or “booster shot” is being employed here to denote both categories.

While there is not sufficient data specifically from India on waning antibody counts, there is enough evidence from the world backing such doses.

Booster shots

India began vaccinating its frontline and healthcare workers on January 16 and opened up the programme to the elderly and immunocompromised on March 1.

More than 69.2 lakh people – over 70% of the eligible population – have received the first dose till now. Of these, nearly 90% have been of Covishield, and the rest of Covaxin, the homegrown inactivated virus vaccine, according to the government’s Cowin dashboard.

While some sections of people may be in urgent need of booster doses, it may not hold true for others, experts argue. “Given the high extent of population seroprevalence after the huge second wave, it may be best to target first and second doses to the entire population before going in for a third dose to frontline and healthcare workers,” said Gautam Menon, professor at the departments of physics and biology at Ashoka University.

In the case of healthcare workers, for instance, India could look at a more nuanced policy.

“Healthcare workers who work with immunocompromised patients could be considered for additional doses,” Parikh recommended. “For instance, oncologists, elderly doctors or those who are clinically vulnerable.”

India may also need to consider supplementing Covaxin, given Strategic Advisory Group of Experts’ latest recommendation for vaccines like Sinopharm and Sinovac, which have demonstrated weakening immunity over time. The WHO has not made a suggestion specific to Covaxin because the brand is not yet listed by the organisation for emergency use.

There is also an ethical dilemma before India now.

Vaccine equity

As a policy, the WHO has objected to countries opting for wide-ranging booster doses.

“In the context of ongoing global vaccine supply constraints, broad-based administration of booster doses risks exacerbating inequities in vaccine access by driving up demand and diverting supply while priority populations in some countries, or in subnational settings, have not yet received a primary vaccination series,” it said in an interim statement on October 4.

Between March and June, when the second Covid-19 wave was raging through India, the government unofficially halted exports, asking manufacturers to focus on domestic demand.

At the time, experts said, the decision made sense. But now, with improved supplies and a lower caseload, India will need to consider its international commitments.

“We have to remember that a bulk of the vaccines globally are manufactured in India, and we have a commitment to supply doses to low- and middle-income countries,” Parikh said. In some countries of Africa and Asia, he said, healthcare and frontline workers have not even received first doses of the vaccines.

This article first appeared on Quartz.