Chennai: Multiple Indian regions could be seeing the impact of vaccination against Covid-19 on the likelihood of getting severe disease in the ongoing third wave, some data released by local governments show. However, analyses of India's latest Covid-19 wave are once again hamstrung by an acute lack of granular data.

On September 9, 2021, the Ministry of Health and Family Welfare's (MoHFW) Indian Council for Medical Research (ICMR) announced that it was launching a vaccine tracker by linking the ICMR's database of Covid-19 tests with the MoHFW's COWIN vaccination database through patient phone numbers. This would allow the ICMR to measure the impact of vaccination status on severe disease and death, Director General Balram Bhargava had said.

The vaccine tracker that was then launched appears to show a graph of weekly data on Covid-19 deaths from April 18, 2021 onwards based on vaccination status as well as age. The summary statistics alongside the tracker claim that the data show 98.4% vaccine effectiveness in preventing mortality from one dose and 99.1% from two doses. These data are, however, 48 days old. November 28, 2021 is the latest day for which data are visible on the IMCR's tracker.

A screenshot of the ICMR's vaccine tracker, accessed on January 14, shows data for the week ending November 28. An archived version of the tracker can be accessed here.

But what precise number of deaths underlies this tracker is unclear, limiting its use for policy and action. In the current surge, for instance, the government does not have these data to draw upon. "We have not analysed the data [on vaccination status of deaths in this wave]…these are generally done more as a sample study," joint secretary Lav Agarwal said at an MoHFW press conference on January 12, 2022. "We are collecting this information," added V.K. Paul, member for health at the central government's policy think-tank, Niti Aayog.

That the ICMR's Vaccine Tracker captures the vaccination status of every Covid-19 death in the country is unlikely, several state-level health administrators said. In Tamil Nadu, for instance, the vaccination status of Covid-19 deaths is available at the hospital-level only and is not maintained at the state level;. when the Union government recently sought these data, they had to be gathered from individual hospitals, Narayana Babu, the state's Director of Medical Education, told IndiaSpend. In Bihar, these data are not available even for past waves, Pratyay Amrit, the state's Additional Chief Secretary (Health), told IndiaSpend. The ICMR directed IndiaSpend's questions to Harpreet Singh, ICMR's Member Secretary and Head of its Division of Biomedical Informatics; we will update the article when he replies.

This would not be the first time that the government had made bigger claims than it had the supporting data for. In April 2021, Bhargava claimed far higher vaccine efficacy than what published research had shown based on what IndiaSpend found to be faulty and misleading data.

What exists, then, are summary statistics shared by some local governments to show that the majority of those with severe disease are the unvaccinated, but without the underlying data being shared.

In Mumbai for instance, data from the city's administration shared with IndiaSpend show that 96% of the 1,900 Covid-19 positive patients admitted on oxygen-supported beds as of January 6, 2022, were unvaccinated. However, given that the city administration reportedly claims that 100% of the population has received at least one vaccine dose, the data raise questions about who these unvaccinated people are, and whether it was just their unvaccinated status that made them more prone to severe illness. "They might be the floating population or those who came in from neighbouring districts to seek treatment," additional municipal commissioner (health) Suresh Kakani told IndiaSpend.

Additionally, data for Mumbai for the last one year show that 94% of Covid-19 deaths since February 2021 were of those who had not received a single dose of the vaccine. However, vaccinations for those aged 60 years and above only began in March 2021, for those aged 45 and above in April 2021 and for those aged 18 and above in May 2021, around the time that deaths in the second wave were already peaking.

In Karnataka, data shared with IndiaSpend by Munish Moudgil, Head of the state's COVID War Room, show that between December 1, 2021 and January 7, 2022, the unvaccinated were ten times more likely to have a symptomatic Covid-19 infection and were 30 times more likely to be in the ICU or the High Dependency Unit than the vaccinated.

In Chennai, 87% of those who died of Covid-19 in August and September 2021, and 69% of those who died of Covid-19 in December 2021 were unvaccinated, city officials said.

For evidence of the impact of vaccination on hospitalisation and death, the government has instead turned to data from other countries. On January 12, Agarwal presented data from New York's State Health Department that showed the difference in daily new Covid-19 cases and hospitalisations among the fully vaccinated and the unvaccinated over time; the US, however, uses more effective mRNA vaccines (such as Pfizer-BioNTech) and has deployed booster shots since September 2021.

"This is really a huge gap in our understanding of the impact of the pandemic in India," Gautam Menon, Professor of Physics and Biology at Ashoka University, and an infectious disease modeller, told IndiaSpend. "For the Omicron variant, there seems to be a growing consensus that vaccinations should protect against severe disease, but we are still completely in the dark regarding hybrid immunity, which most adults across India might be expected to have, given the impact of the second wave," Menon said. Hybrid immunity refers to the combination of immunity acquired both from prior infection and vaccination. About 74% of Indian adults were found to have Covid-19 antibodies either through prior infection or vaccination, or both, by mid-July 2021, per the MoHFW's fourth nationwide Covid-19 serosurvey, IndiaSpend reported in July 2021.

"Extrapolating from results in other countries, which use different vaccines and have different backgrounds of seropositivity, both from infections and vaccinations, may simply not be useful in the Indian context. This lack of data prevents reasonable estimates from being made of, for example, the number of cases that might require ICU care at any stage of the ongoing Omicron wave and the resulting potential stress on the health care system," added Menon.

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