The director of the Center for Disease Prevention and Control in the United States, Rochelle Walensky, said that new data suggests that people vaccinated against COVID-19 with both doses almost never transmit the coronavirus.
“Our data from the CDC currently suggests that vaccinated people don’t carry the virus, they don’t get sick, and that’s not just in clinical trials but in real-world data,” Walensky said in an interview with MSNBC.
The study referred to by Rochelle Walensky involved 4,000 front-line health workers, some vaccinated and some unvaccinated, who were tested weekly to see if they were infected with COVID-19 between December last year and March this year.
Thus, only three cases of infection were detected among people vaccinated with both doses, while 161 of the participants who were not vaccinated were infected with COVID-19.
In other words, vaccination with the two doses of the vaccine developed by Pfizer-BioNTech and Moderna completely eliminated detectable infections. The AstraZeneca vaccine has not yet been approved in the United States.
Following the study, the CDC concluded that Pfizer and Moderna vaccines reduce COVID-19 infections by 90%.
More data is needed to reach a clear conclusion, which is why US researchers are currently recruiting thousands of students to learn more about the chances of the virus spreading among vaccinated people.
As vaccination becomes more widespread, researchers should be able to discern the effect on infection and transmission patterns, although it can be difficult to distinguish the impact of inoculations from that of measures such as lockdowns and mask mandates. The completion of the vaccine trials testing for asymptomatic infections will bring additional information.
Two trials are expected to finish in April. However, one is of a vaccine from China’s Sinovac Biotech Ltd., which has a reported efficacy rate as low as 50% against symptomatic disease. The other tests the Russian Gamaleya Research Institute’s shot, whose efficacy rate against symptoms was 92% in clinical trials, but it’s a small study.
September should bring the completion of sizable trials of highly efficacious vaccines. Results for the shots that have proved most effective at preventing disease (95%), from Moderna and Pfizer-BioNTech, aren’t expected until October 2022 and January 2023, respectively.