Among those in the study without previous SARS-CoV-2 infection who had received the Pfizer/BioNTech vaccine, patients with severe obesity had antibody levels more than three times lower than normal-weight individuals.

Among recipients of Sinovac Biotech's CoronaVac, those with severe obesity and no history of prior infection had antibody levels 27 times lower than normal weight people, according to data being presented this week at the European Congress on Obesity in Maastricht, Netherlands. By comparison, in the 70 volunteers with a previous coronavirus infection, antibody levels were similar in people with and without severe obesity.

Meanwhile, South African researchers have found that infection with the Omicron variant of the coronavirus can significantly improve the immune system's ability to protect against other variants, but only in people who have been vaccinated.

In unvaccinated people, an Omicron infection provides only "limited" protection against reinfection, they reported on in Nature last week.