‘Erroneous to conclude we have attained herd immunity’

The fourth sero survey conducted across India found that on an average 67.6% of the population has been infected. Also, over 25% of people have been vaccinated with one dose. In an email, Dr. Srinath

The fourth sero survey conducted across India found that on an average 67.6% of the population has been infected. Also, over 25% of people have been vaccinated with one dose. In an email, President of the Public Health Foundation of India and member of the National COVID-19 Technical Taskforce dispels the wrong notion that India is close to reaching herd immunity and explains the uncertainty of protection even among those already infected. Scientists from ICMR have themselves clarified that this survey is not representative of the whole country. They have called for state level, preferably district level, surveys across the country using standardised methodology. If we wish to have a truly nationally representative survey, we must sample from every postal code area in the country. That will be highly resource intensive and not feasible during a pandemic period when health system has many competing demands. The national surveys of ICMR are valuable, even if they are not fully representative of the whole country. By conducting repetitive surveys in the same districts, these studies provide information on how proportions of infected people in the population have increased over time. That helps us to understand how effective our efforts to contain viral transmission have been during the periods between surveys. Kerala, for example, has a low level of seroprevalence because they have adopted public health strategies which slow down transmission. While the survey results are also interpreted to estimate the numbers of immune and susceptible persons in the population, there are reasons to question those assumptions.