The study, published in the New England Journal of Medicine on June 15, examined the Omicron wave in Qatar from December 2021 to February 2022, comparing vaccination rates and immunity among more than 100,000 infected and non-infected individuals. with Omicron. The study authors found that those who had a previous infection but had not been vaccinated were 46.1 and 50 percent immune to the two subtypes of the Omicron variant, even more than 300 days after the previous infection. However, people who received two doses of the Pfizer and Moderna vaccines but had no previous infection were found to be negatively immune to the BA.1 and BA.2 Omicron subtypes, indicating an increased risk of COVID-19 infection in the average person. More than six months after receiving two doses of the Pfizer vaccine, immunity to any Omicron infection was reduced to -3.4%. But for two doses of the Moderna vaccine, immunity to any Omicron infection dropped to -10.3 percent more than six months after the last injection. Although the authors reported that three doses of the Pfizer vaccine boosted immunity by more than 50 percent, it was measured just over 40 days after the third vaccination, which is a very short time. By comparison, natural immunity remained at about 50 percent when measured more than 300 days after the previous infection, while immunity levels dropped to negative numbers 270 days after the second dose of the vaccine. These data indicate a risk of reduced immunity to the third dose of the vaccine as time goes on. The findings are supported by another recent study from Israel, which also found that natural immunity declines significantly more slowly than artificial or vaccinated immunity. The study found that both natural and artificial immunity decreased over time. People who had been previously infected but had not been vaccinated had half the risk of re-infection compared to those who had been vaccinated with two doses but had not been infected. “Natural immunity wins again,” wrote Dr. Martin Adel Makari, a public policy researcher at Johns Hopkins University, on Twitter, referring to the Israeli study. “Among individuals previously infected with SARS-CoV-2, protection against re-infection decreased as time went on,” the authors concluded, “however, this protection was two-dose vaccine. Enrico Trigoso contributed to this report.
