Two studies looking at important topics related to COVID-19 were recently published that look at the effectiveness of natural immunity to SARS-CoV-2 and the effectiveness of masks, respectively.
Israel natural immunity vs. vaccine-induced immunity study
A study by researchers from Tel Aviv conclude that natural immunity to SARS-CoV-2 infections is more robust against the Delta variant than two doses of the Pfizer-BioNTech vaccine BNT162b2.
The preprint (not peer reviewed) was published on Medrxiv.
In the large Israeli retrospective cohort study, thousands of medical records were looked at with an examination of documented RT-PCR confirmed SARS-CoV-2 infection, COVID-19-related
hospitalization and death. Outcomes were evaluated during the follow-up period of June 1 to August 14, 2021, the date of analysis, corresponding to the time in which the Delta variant became dominant in Israel.
They conclude that natural immunity affords longer lasting and stronger protection against infection, symptomatic disease and hospitalization due to the Delta variant of SARS-CoV-2, compared to the BNT162b2 two-dose vaccine-induced immunity. Notably, individuals who were previously infected with SARS-CoV-2 and given a single dose of the BNT162b2 vaccine gained additional protection against the
Infectious disease experts caution that intentional infection among unvaccinated people would be extremely risky and that the vaccine is highly protective against severe disease and death.
The study shows the benefits of natural immunity, but “doesn’t take into account what this virus does to the body to get to that point,” says Marion Pepper, an immunologist at the University of Washington, Seattle.
Bangladesh mask study
A large, randomized trial led by researchers at Stanford Medicine and Yale University has found that wearing a surgical face mask over the mouth and nose is an effective way to reduce the occurrence of COVID-19 in community settings.
The study was published in Innovations on Poverty Action.
The researchers enrolled nearly 350,000 people from 600 villages in rural Bangladesh. Those living in villages randomly assigned to a series of interventions promoting the use of surgical masks were about 11% less likely than those living in control villages to develop COVID-19, which is caused by infection with the SARS-CoV-2 virus, during the eight-week study period. The protective effect increased to nearly 35% for people over 60 years old.
There were significantly fewer COVID-19 cases in villages with surgical masks compared with the control villages. (Although there were also fewer COVID-19 cases in villages with cloth masks as compared to control villages, the difference was not statistically significant.) This aligns with lab tests showing that surgical masks have better filtration than cloth masks. However, cloth masks did reduce the overall likelihood of experiencing symptoms of respiratory illness during the study period.