Real-life data offers hope that mRNA vaccines are highly effective in limiting infection and suspected transmission of the coronavirus, in addition to their well-known ability to prevent symptoms of covid-19. The findings, based on research from Israel and elsewhere, are good news as they contain the pandemic sooner rather than later.
An investigation published in the Lancet last week looked at health workers at Israel’s Sheba Medical Center. The study compared the rates of covid-19 – both with and without symptoms – among workers who did or did not receive the Pfizer / BioNTech vaccine. As other research has shown, people were significantly less likely to contract covid-19 after receiving the first of two scheduled doses.
Within two to three weeks after the first dose, the risk of symptomatic covid-19 was reduced by 85%. Important is the risk of covid-19 in general, including asymptomatic infection, in which a person has the virus but does not feel sick was also reduced by 75% over the same period, based on regular PCR testing. This is crucial because even people with silent infections can still transmit the virus to another person. But if a vaccine largely prevents people from getting sick and from carrying enough of the virus to test positive, it means that it also lowers the risk of virus transmission from a vaccinated person to others.
The results of another recent study, not yet published, appear to show an even greater benefit for fully vaccinated people in Israel. Based on data analyzed by the Israeli Ministry of Health, Reuters reported last Thursday, the risk of infection was reduced by 89% in people who received two doses of the Pfizer / BioNTech vaccine.
A preliminary study in the US released last week by researchers at the Mayo Clinic points to similar benefits to the Moderna vaccine. They looked at workers at the Mayo Clinic and related health centers who had received the first dose of an mRNA vaccine at least 36 days earlier. Compared to their unvaccinated colleagues, the workers were 89% less likely to test positive for covid-19 after receiving both doses.
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Many experts were cautious about claiming that covid-19 vaccines will reduce transmission, arguing that the data just wasn’t available yet to know for sure. But other experts have argued that it would be very unusual for a vaccine effective in preventing disease to have no effect on reducing transmission and it is not useful to worry about an unlikely outcome. In any case, the proofs of this are and other studies should be reassuring for everyone.
More research will be done to understand how effective the mRNA vaccines are at preventing transmission. Other vaccines are based on different technologies, and some are less effective than the mRNA vaccines in preventing disease, so they will also need to be studied carefully. And the spread of new coronavirus variants could complicate matters, as at least some vaccines have been shown to be less effective against certain variants.
That said, this is no doubt good news if you are hoping the pandemic will end as soon as possible. Vaccines that prevent covid-19 disease and transmission will only make it more difficult for the coronavirus to spread as a greater proportion of the population is vaccinated, and they should speed up the time it takes for life to recover. turn to some semblance of normal.