China’s Covid-19 surge is unlikely to affect India

As reports about Covid-19 raging in China go from a trickle to a flood, my phone has been buzzing with pings from friends anxious to know whether forthcoming holiday plans need to be revised. Despite the turmoil across the border and a somewhat fuzzy crystal ball, I feel confident enough to advise against panicked cancellations and add that a little bit of extra caution should suffice. The reason for this confidence is data, perhaps not as much as I desire, but much more than we have ever had for any other disease in history. Such data goes far beyond official counts on government websites and includes published serosurveys, consensus models of actual numbers of infections and deaths, neutralisation data for multiple variants, protective effects of vaccines and prior infections, and wastewater surveillance, among others. Despite the relative lack of Chinese data — requiring the use of surrogate data from Hong Kong — and multiple conflicting stories within the Indian data, two very different pictures emerge for the two Asian giants.First, natural immunity. After the initial Wuhan outbreak in 2020, China had mostly successfully adopted a zero-Covid policy. In Hong Kong, before the Omicron BA.2 outbreak in early 2022, only a tenth of the population had been infected. It is likely that the fraction in mainland China with natural immunity is also that low. In contrast, in Indian cities, nine-tenths of the people were already infected before Omicron, based on serosurveys. This is the main reason why the Omicron wave was not severe in India. Now, after Omicron, the fraction of previously infected people is close to 100%, with most people having been first infected with Delta and then reinfected with Omicron, based on serial serosurvey data with variant-specific neutralisation assays. Most of these infections are recent and with an Omicron lineage (BA.2) relevant to currently circulating lineages. Thus, there is extremely high natural immunity in India, the cost of which was paid during the Delta wave. There is good data that recovery from the first episode of Covid-19 confers about 95% protection from future Covid-related severe disease or death for at least two years. This explains why the countries that fared poorly during the Delta wave or earlier Omicron waves, are not seeing many severe outbreaks anymore.Second, vaccine immunity. The preferred route to immunity is vaccines, not infection. However, none of the ancestral-strain vaccines confer good protection against Omicron infection and new bivalent vaccines that provide better protection against Omicron infection are not available in India or China. While two doses of all vaccines have been effective against severe disease or death in young people without comorbidities, significant differences start emerging for the elderly, where the vaccines most used in India (Covishield, an adenoviral DNA vaccine) seem superior to those used in China (CoronaVac and Sinopharm, inactivated virus vaccines). Additionally, the Indian vaccination programme mostly picked up pace after the Delta wave, leading to strong hybrid immunity, combining both natural and vaccine-induced immunity.Third, vulnerable population. The last but perhaps most critical difference is that while both India and China are similarly populous, India is a younger nation. For very old people at the highest risk of death from Covid-19, the difference is very large. There are 30 million Chinese aged above 80, but only about five million Indians in the same age demographic. The toll of an Omicron wave, as seen in Hong Kong earlier this year, is disproportionate in the previously uninfected, unvaccinated, or inadequately vaccinated elderly. There is excellent data with inactivated Chinese vaccines that show that good protection is reached only after the third dose, yet less than half of the elderly seem to have been sufficiently vaccinated in China.And four, variants. Virus-sequencing data from China is sparse, with Omicron BF.7 seen to be rising before the current wave. This variant has already circulated in many countries, including India, but was unable to displace the more immune-evasive Omicron variants such as XBB (dominant in India) and BQ.1 (dominant in the West). Earlier, the BA.5 Omicron variant circulated in India without any increase in severe disease but is now driving ongoing waves in Japan and South Korea. Until we see a new strain of Sars-Cov-2, entirely different from Omicron, the risk of any new variant must be assessed locally, based on previous waves of infections and local vaccination practices. Variant-driven waves of infection in one country may have no impact in another country with sufficient immunity to that variant. Thus, ongoing Omicron waves in China or Japan or Korea are unlikely to lead to a major one in India, which has recent immunity. This will change if an entirely new variant arises, but as of now, there is no such evidence and genomic surveillance has been enhanced.Today, deep data allows more precise decision-making, whether for an individual or a nation. Precision in public health, driven by the Covid-19 pandemic, is the best way forward. To me, the much higher hybrid immunity of India, a smaller vulnerable population, absence of any new variants on sequencing, the previous failure of BF.7 to rise in India, and lack of any increase in Sars-CoV-2 viral loads in city wastewater, suggest that there is little imminent danger of a new surge of severe cases. Knowledge gaps about what is happening in China makes it important to re-evaluate as new data comes. What World Health Organization chief Tedros Adhanom Ghebreyesus said two years ago is unfortunately still true, “We may be tired of Covid-19, but it is not tired of us”. Till then, we should make appropriate efforts to protect the vulnerable and enjoy the holidays.Anurag Agrawal is dean, BioSciences and Health Research, Trivedi School of Biosciences, Ashoka University The views expressed are personal