India on Wednesday approached a billion doses of Covid-19 vaccines administered, but the daily targets required to fully vaccinate all adults by December 31 have increased from 8.9 million in mid-July to 12.3 million now.

Health experts say the increase in the target daily dose probably reflects gaps between the volume of doses the Centre had expected to be available and what has actually been available up to the eve of the milestone one billionth dose.

India needs 1,888 million doses to inoculate all its estimated 944 million adults with the two doses required for full vaccination.

The CoWIN digital platform that helps manage the Covid-19 vaccination campaign on Wednesday displayed a counter with the title “India counting to 1 billion doses”, showing the country at 5.40pm was 4,637,186 doses away from its one billionth dose.

The campaign had by Wednesday evening administered nearly 996 million doses and would need to administer 892 million doses over the remaining 72 days of the year to meet the projected goal of vaccinating all adult Indians by the end of the year.

The Union minister of state for health, Bharati Pravin Pawar, on Wednesday reaffirmed the Centre’s goal of vaccinating all adults by December 31.

“More than 99 crore (990 million) doses of Covid-19 vaccines have been administered in the country and the government has set a target of vaccinating the country’s entire adult population by the end of the year,” Pawar told a healthcare event organised by the Federation of the Indian Chambers of Commerce and Industry.

The campaign will have to administer around 12.3 million doses daily on an average to complete full adult vaccination by December 31, an increase from the calculated daily target dose of 9.8 million on August 19 and 10.5 million on September 20.

Health experts say the campaign’s pace in October has been less than half what it should have been to complete full vaccination by December 31.

The average daily doses administered rose from 4.3 million in July to 5.9 million in August to 7.8 million in September, but have been less than 6 million during October so far.

The Union health ministry had in June projected an anticipated availability of 1,350 million vaccine doses — 500 million Covishield, 400 million Covaxin, 100 million Sputnik, 50 million doses of a Zydus Cadila vaccine and 300 million doses of a vaccine from Bio E.

But the campaign has even until mid-October remained almost entirely dependent on Covishield and Covaxin. Among the nearly 996 million doses administered until Wednesday evening, Sputnik V accounted for only around 1 million.

The health ministry is yet to introduce the Zydus Cadila vaccine into the campaign and India’s drug regulatory authority is yet to approve Bio E’s vaccine. A Bio E spokesperson contacted by this newspaper declined to discuss the current regulatory status of the company’s vaccine.

Health experts say this puts a question mark on the 300 million doses of the Bio E vaccine which the health ministry had factored in to calculate the figure of 1,350 million doses.

Some public health experts had earlier this year predicted that vaccine hesitancy or difficulties in accessing vaccines for certain sections of the population could at some point begin to limit the uptake of doses. But the nationwide counts of first doses still remain similar to the numbers of second doses. For instance, on Wednesday, the campaign administered over 3.7 million first doses and nearly 2.9 million second doses.