Number Theory: How vulnerable is India to a third Covid wave?
The seven-day average of daily new Covid-19 cases in India has been rising in the past two weeks – from 37,975 in the week ending July 22 to 40,710 for the week ending August 3.
That isn’t a significant increase in absolute terms but it has still given rise to questions on whether India is witnessing the beginning of a third wave of Covid-19 infections, and, if so, whether this wave will be as severe as the second?
Three factors will determine the answers: pace of vaccinations, regional and demographic variations in vaccination, and presence of antibodies in the population.
1. The country’s vaccination progress so far
According to data from the Co-WIN dashboard, around 40% of India’s adult population – 375 million out of a projected population of 940 million – has received at least one dose of a Covid-19 vaccine as on August 3. The share of population which has received both doses is much lower, 11%. This number is expected to increase faster as more people become eligible for their second dose of vaccination, as reported in a July 17 story by Jamie Mullick.
Is India’s current vaccination progress enough to slow down a Covid-19 wave? Perhaps not. After all, more than half of the population in the US and UK has been fully vaccinated and cases have started rising at a rapid pace in both countries, largely due to the Delta variant of the coronavirus. Where vaccines have helped is in bringing down deaths, as is clear from a comparison of deaths in the adequately vaccinated West and poorly vaccinated Asian and African nations.
2. The threat of community transmission remains
Research shows that even one dose of Covid-19 vaccine offers some protection against even the Delta variant. So, the fact that at least 40% of India’s population has received at least one dose is good news. The headline number should be read with a caveat, though. India opened its vaccination drive for different age-cohorts at different times. It was opened on March 1 for those above 60 years, April 1 for those between 45-60 years and only on May 1 for the 18-44 years age group.
These factors, and the extended gap between doses for the vaccine most used in India (Covishield; at least 12 weeks) have resulted in the older cohort having an edge in the share of the vaccinated population. The share of population which has received at least one dose of the vaccine was 27.6% in the 18-44-year-old age group, compared to 55.9% for those over the age of 60.
The younger population is more likely to venture out and be potential carriers of the virus. The Time Use Survey conducted by the National Statistical Office (NSO) in 2019 lists eight different activities that are directly related to travelling – from commuting for work or studies to travelling for leisure or self-care activities. Most people between the ages of six and 54 travelled on average for around 40 minutes in a day in 2019. This dropped to 32.6 minutes for 55-64 year olds and just 19.9 minutes for those in the 65 and above cohort.
This means that India’s vaccine protection against community transmission could be lower than what the headline vaccination numbers suggest.
3. Huge disparity in vaccination coverage across states
The other factor worth taking note of is the difference across states in the share of population which has received at least one dose of vaccine. There is a wide variation on this count: Himachal Pradesh has vaccinated more than 73% of its population, while Bihar and Uttar Pradesh have managed to vaccinate less than 30%. This also means that the states at the bottom of the vaccination ladder will be more vulnerable to a third wave. It is on this count that there is some relief for Kerala, which is contributing around half of the total daily new cases but has vaccinated more than 55% of its eligible population.
There are no population projections for districts. However, even coverage with respect to the total population of a district in the 2011 Census shows the difference in coverage among districts. The top 128 of 640 districts have administered at least one dose of the vaccines to 43% of their total population. States with most number of districts of this kind are the ones that are doing well overall. The highest number of such districts (12) are from Himachal Pradesh, followed by 11 from Arunachal and Jammu and Kashmir, and 10 from Uttarakhand. No district in Bihar, Jharkhand, or Andhra Pradesh has this level of coverage. The least vaccinated 128 districts have at least partly vaccinated 12.2%-21.6% of their population. 43 of these districts are from Uttar Pradesh, 29 from Bihar, and 12 from West Bengal – the states that lag the most in overall vaccinations. The five districts with the least coverage are Senapati in Manipur (12.2%), Mewat in Haryana (12.6%), Rae Bareli (12.7%) and Badaun (12.8%) in Uttar Pradesh, and Mahbubnagar (13%) in Telangana. The entire population in New Delhi, the Central district of Delhi, Daman and 95% of the population in Gurugram and Dadra and Nagar Haveli have received at least one dose of the vaccine.
4. What about likely antibody immunity from 2nd wave?
Antibodies in infected patients are believed to grant temporary immunity against infections. It is on this count that India may have an advantage even as it scrambles to reach a critical mass of vaccinated population. The latest sero-prevalence survey, which was conducted by the Indian Council of Medical Research (ICMR) in June-July showed a big spike in the prevalence of antibodies: from 24% in December-January to 67.6% in June-July. The second wave of Covid-19 infections, as per the seven-day average of daily new cases, peaked on May 9. The fact that Kerala has the lowest prevalence of antibodies in the latest sero-survey and is also witnessing the most new infections in the country right now suggests that states with higher antibody levels could enjoy some protection against a new wave of infections.