Indian Researchers Find that Natural Immunity Protects Better Against Infection than the AstraZeneca Vaccine

I’ve already covered three studies that found natural immunity protects better against infection than the vaccines. These comprise two from Israel, and one from Denmark. In each case, individuals who’d already had Covid were much less likely to become infected than those who’d been vaccinated.

Now a fourth study has come to my attention; this time from India. (The study was published as a preprint back in August.)

Malathi Murugesan and colleagues monitored infections in a cohort of healthcare workers between April and June of this year, during the country’s second wave. They compared four groups, corresponding to the different combinations of previously infected or not, and vaccinated or not.

Note: the vast majority of participants had received the AstraZeneca vaccine. This is in contrast to the Israeli and Danish studies, where most individuals had received another vaccine (mainly Pfizer).

Among those who hadn’t been previously infected or vaccinated, the cumulative infection rate was 14.9%. It was slightly lower among those’d been vaccinated but not previously infected, namely 11.1%. And it was dramatically lower among those who’d been previously infected: 2.1% among those who hadn’t been vaccinated, and 1.4% among those who had.

To check these results were robust, the authors ran a statistical model controlling for age, sex, type of work, and the daily incidence of Covid in the surrounding area (the city of Vellore in Southern India).

They estimated the protective effect of natural immunity to be 86% (which is consistent with a recent systematic review). By contrast, vaccine effectiveness was only 32%. As expected, the protective effect of hybrid immunity was 91% – slightly better than that of natural immunity alone.

There are now four separate studies all showing the same thing: several months after the corresponding event, natural immunity provides substantially better protection against infection than the vaccines.

“Vaccination efforts,” the Indian researchers note, “should be optimised by directing vaccination towards the areas where individuals are non-immune.” In other words, there was no need to vaccinate healthy people who’d already had Covid; those vaccines should have gone to the clinically vulnerable in poor countries.