The Covid-19 vaccination campaign has saved over 275,000 lives and averted 1.2 million hospitalisations in the US, researchers have estimated through a study that independent experts said India would find difficult to undertake at this point because not enough people are vaccinated.

The study by infectious disease epidemiologists at Yale University and other academic institutions is the first to evaluate nationwide cases, deaths and hospitalisations averted by the vaccination campaign in the US in the face of highly transmissible coronavirus variants.

“Our results demonstrate the extraordinary impact of swift vaccination for averting cases, hospitalisations and deaths,” Alison Galvani, a professor of epidemiology at Yale, and her colleagues said in the study, not peer-reviewed yet but posted on medRxiv, an online repository for preprints.

Health officials have often described India’s vaccination campaign as among the fastest in the world, pointing out that the US took 193 days to administer 320 million doses while India took only 163 days.

But health experts in India who have seen the US study said the number of doses administered daily is less important than the proportion of the population protected.

“It is not the number of the doses given daily that really matters, but the proportion of the population protected fully,” said Oommen John, a physician and research fellow at The George Institute for Global Health, New Delhi.

The US has fully vaccinated over 48 per cent of its population with the two required doses, while India has so far vaccinated only 7 per cent of its eligible population with two doses.

India is “sadly” quite a distance from even trying to make such assessments, said another senior medical researcher who is a member of an expert panel guiding India’s Covid-19 response.

It is “too early” to conduct such a study in India, an adviser to the government’s Covid-19 vaccination campaign told The Telegraph.

Poor planning and lack of early investments have meant India’s vaccination campaign has been slower than it could have been. The campaign has so far administered over 370 million doses but requires over 1,500 million doses to fully vaccinate an estimated 944 million currently eligible people.

Health officials have expressed confidence that India’s stocks of doses will grow significantly — through both ramped up production and new vaccines — between August and December to complete the task by the year-end.

The US researchers examined the impact of vaccinations taking into account the population demographics and transmission features of circulating coronavirus variants, among other factors. They also simulated two “counterfactual scenarios” — no vaccinations at all and an inoculation campaign running at half the actual pace.

Their study has estimated that the vaccination campaign has potentially averted 26 million Covid-19 cases, 1.25 million hospitalisations, and 279,000 deaths in the US between the campaign’s start on December 12, 2020, and June 28 this year.

The researchers said vaccination prevented a large surge during April 2021 when the US could have experienced around 4,500 deaths during its peak, a toll that would have likely exceeded the 2020-21 winter surge because of the highly-transmissible Alpha variant.

As new variants — including the Delta variant that was first detected in India — surge among unvaccinated people, Galvani and her colleagues have said, there is a need for an intensified campaign, particularly in areas with low vaccination rates.

“Even low vaccination coverage such as in India would have a high impact on averting severe Covid-19 and deaths,” Pratha Sah, an associate research scientist at Yale and study team member, told this newspaper. “It should be possible to assess such impacts of vaccination in India too.”

An exercise to estimate nationwide cases and deaths averted may not be as meaningful in the early phase of the vaccination campaign when coverage is low. “This is because the impact of vaccination is hard to distinguish from other population-level changes,” said Abhishek Pandey, a team member at Yale. “But since 30 per cent of people in India have received first doses, it should be feasible to evaluate its impact on the ongoing Covid-19 situation in India.”

John at the George Institute said India could have initiated an exercise to evaluate the real world effectiveness of vaccines in the early weeks of the vaccination campaign. Over 290 million people in India have received a single dose and over 70 million have received both doses.

“If we had designed and implemented a real-world vaccine effectiveness evaluation exercise, we could have gained some insights about the vaccines’ nationwide impact in India,” John said.