A report by the Finance Ministry has said that that 85 per cent of the population aged 45 and above has acquired immunity against severe illness due to Covid.
“As 85 per cent of the most vulnerable 45-plus population has developed immunity against severe illness due to Covid, the impact of subsequent waves on hospitalisation and deaths may be limited even though these waves may cause an increase in infections.
“The attention must, therefore, be directed to similarly enhancing immunity among the children and adults in the 18-44 age groups,” said the Monthly Economic Report by the Economic Affairs Department.
Necessary precautions
Further, it advised that till 85 per cent of the population below 44 years age develops immunity, the necessary precautions and Covid-appropriate behaviour must accompany normal economic activities.
Also, “State governments must take the initiative in conducting district-level sero-prevalence surveys so that they can direct their vaccination efforts optimally”, it said.
The report used ICMR’s sero-prevalence study of June-July, along with vaccination numbers, for its arguments. It countered doubts about the veracity of ICMR study by taking the example of Mumbai.
This cosmopolitan recorded about 90 per cent of new infections during the second wave among those living in high-rise buildings, where sero-prevalence in December 2020 was 16 per cent. However, slums with sero-prevalence of 57 per cent recorded just 10 per cent of new infections.
“This demonstrates the strong negative correlation between sero-prevalence and new infections,” said the report.
Antibodies
It further drew an inference that the presence of antibodies did reduce significantly the likelihood of infections in the second wave, even to the Delta variant.
Quoting various research reports and studies, it mentioned various observations – the likelihood of reinfection once an individual is already infected is extremely low, and that antibodies developed from infection remain active for at least six months. “Even if the sero-prevalence was measured in June, the antibodies developed should remain active till at least the end of this calendar year. By the end of the calendar year, India has targeted to vaccinate its adult population,” the report mentioned.
It also noted a recent research report (authored by Sharifa Nasreen and others published in medRxiv), which estimated the effectiveness of 1 dose of the ChAdOx1 vaccine (popularly known as Covishield), and found that its effectiveness against the Delta variant was similar to that against Alpha variant.
In order to estimate the proportion of the population with immunity across age groups as of July, the report used the estimate from the ICMR survey that 81 per cent of the individuals that received one dose already have the antibodies.
Similarly, 89 per cent of the individuals that received two doses already have the antibodies. These estimates are required to avoid any double counting. Accordingly, it concluded about part of population acquiring immunity against severe illness due to Covid. “As 90 per cent of deaths have occurred in the 45-plus population, they are unlikely to be vulnerable to a third wave,” it said.