Future Covid waves may be less deadly, but your immunity won't be perfect, says top infectious disease expert

Faheem Younus, chief of infectious diseases at the University of Maryland, UCH, said having a large pool of vaccinated and Covid-19-recovered people in India means the severity of illness in any future surge in coronavirus infections in the country is likely to be less compared with the 2020's Delta wave. In an interview with Teena Thacker, Younus said he's not sure when the pandemic will end. Edited excerpts:

Do you think a milder wave means an end of the pandemic?

We do not know. Due to billions of people vaccinated and millions of people more recovered from Covid-19, future waves are likely to be less deadly.

India is giving the same precaution doses as the primary vaccine. Do you think mix-and-match works better?

There is data from a Spanish study that people who received the AstraZeneca vaccine (or Covishield), develop better immunity when they were boosted with a single shot of Pfizer. Similar studies exist between Pfizer and Moderna when they were used interchangeably. Despite these data, I do not think it means that getting boosted with the same vaccine that you received in the primary series will be any inferior. I received Pfizer as my initial series and then received a Pfizer booster.

Given that India had Delta and then vaccination, will it mean less infections in the future? Does hybrid immunity work?

People who are recovered from the Delta variant clearly will have some degree of immunity against Omicron, and even the future variants. But it is important to know that it will not be perfect immunity. In New York State we have seen 3.4% reinfections of Omicron in patients who had previously recovered from Delta. When you look at your numbers, that 3.4% amounts to 170,000 people.I anticipate that due to a large population of vaccinated and Covid-19 recovered people in India, future waves should not cause the same mortality and devastation that Delta did. However, a more transmissible virus like Omicron can very quickly overload the healthcare systems and, therefore, our best option is to keep vaccinating as many people, as quickly as we can, and provide boosters wherever applicable.

If vaccine immunity wanes in 6 months, will we have to keep injecting boosters?

I do think this will end. At some stage we will have better control over this pandemic. Globally, that may happen in 1 year or 5 years; we do not know. At that time the need for annual booster shots will be reassessed.