Real-world data provide hope that mRNA vaccines are extremely effective in limiting infection and likely transmitting coronavirus, in addition to their already known ability to prevent covid-19 symptoms. The findings, based on research in Israel and elsewhere, are good news for the containment of the pandemic sooner rather than later.
A study published In the Lancet last week they looked at health workers at Sheba Medical Center in Israel. The study compared the rates of covid-19 – both with and without symptoms – among workers who received 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 of the first dose, the risk of symptomatic covid-19 was reduced by 85%. Importantly, the risk of covid-19 in general, including asymptomatic infection, in which a person has the virus but does not feel bad, it was also reduced by 75% over the same period, based on regular PCR testing. This is crucial, because even people with silent infections can transmit the virus to another person. But if a vaccine largely prevents people from getting sick and from carrying enough virus to give positive results, it also means that the risk of transmitting the virus from one vaccinated person to others decreases.
The results of another recent study, not yet published, seem to show an even greater advantage for fully vaccinated people in Israel. Based on data analyzed by the Israeli Ministry of Health, Reuters reported on Thursday, the risk of infection was reduced by 89% in people who received two doses of Pfizer / BioNTech vaccine.
In the US, a preliminary study freed last week by researchers at the Mayo Clinic indicates similar benefits for the Moderna vaccine. They looked at workers at the Mayo Clinic and associated health care centers who received the first dose of mRNA vaccine at least 36 days before. Compared to their unvaccinated colleagues, workers were 89% less likely to test positive for covid-19 after receiving both doses.
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Many experts have been cautious that covid-19 vaccines will reduce transmission, arguing that the data were simply not yet available to know for sure. But other experts have done it supported that it would be very unusual for a vaccine to be effective in preventing disease to have no effect on reducing transmission and that it is not useful to leave people worried about an unlikely outcome. In any case, the evidence in them and other studies it should be reassuring for everyone.
Further research will be continued to understand how effective mRNA vaccines are in preventing transmission. Other vaccines are based on different technologies, and some are less effective than mRNA vaccines in preventing disease, so they will also need to be studied closely. And the spread of new variants of coronavirus can complicate things, because at least some vaccines have been shown to be less effective against certain variants.
That being said, this is undoubtedly good news if you hope for the end of the pandemic as soon as possible. Vaccines that prevent covid-19 disease and transmission will make it more difficult to spread the coronavirus as more people are vaccinated and should speed up the time it takes to return to a certain appearance of normalcy.