Why India has not witnessed any surge in cases for months Premium

Daily cases are low despite the newer Omicron subvariants, recombinants possessing greater immune escape and transmissibility

The third wave in India that began in the first week of January 2022, driven primarily by the BA.1 Omicron sub-lineage, peaked at around 3,38,000 new infections on January 21, and came to an end by the first week of March 2022. Except for a short period — mid-June to mid-August — after the third wave, India has not witnessed even an uptick in new infections in 2022. The relative calm in India comes even when new Omicron subvariants and recombinants with ever increasing ability to evade immune responses and greater transmissibility have emerged at regular intervals last year and have led to sudden surge even in hospitalisations and deaths in many countries.

While low levels of testing might wrongly indicate low virus spread in the population, the low test positivity rate and low levels of the virus in wastewater or sewage water surveillance strongly suggest that virus circulation is indeed low in India.

“The hybrid immunity — natural infection and vaccination induced immunity — is the reason that there has not been an uptick in COVID-19 cases in India. An estimated 95% of India’s population above 12 years of age has developed hybrid immunity. India’s situation of hybrid immunity is arguably the best possible protection against SARS-CoV-2,” says Dr. Chandrakant Lahariya, consultant physician and an epidemiologist.

Citing a systematic review published recently in  The Lancet, Dr. Giridhara Babu, epidemiologist at the Public Health Foundation of India, Bengaluru, says hybrid immunity from vaccination (both primary, and primary plus booster dose) and previous infection has provided sufficient protection against reinfection for people in India.

“Individuals with hybrid immunity had the highest magnitude and durability of protection [against Omicron variant], and as a result might be able to extend the period before booster vaccinations are needed compared to individuals who have never been infected,” says  The Lancet review.

Explaining the absence of surges last year, Dr. Vinod Scaria, a senior scientist at Delhi’s Institute of Genomics and Integrative Biology (CSIR-IGIB), says that though greater immune escape by Omicron subvariants indeed make people susceptible to reinfections, the resulting infection is self-limiting and most often asymptomatic, thus possibly not being tested or recorded. 

What makes the absence of new infections surging after the third wave ended is the relative ease with which the Omicron subvariant BA.2.75, which was first detected in India, caused cases to spike between mid-June and mid-August last year; the subvariants and recombinants of Omicron that emerged after BA.2.75 have even greater immune escape and transmissibility but have not caused any spike in cases.