Real-world data offer hope that mRNA vaccines will be highly effective in limiting coronavirus infection and presumably transmission, in addition to its already known ability to prevent covid-19 symptoms. The results, based on research from Israel and elsewhere, are good news for containing the pandemic sooner rather than later.
A study published at the Lancet, last week they examined health workers at Israel’s Sheba Medical Center. The study compared covid-19 rates, 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 take covid-19 after receiving the first of the scheduled doses.
Two to three weeks after the first dose, the risk of having symptomatic covid-19 was reduced by 85%. It is important to highlight the risk of covid-19 in general, including asymptomatic infection, in which a person has the virus but does not feel sick, it was also reduced by 75% in that same period, based on regular PCR tests. 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 i carrying enough virus to test positive means that it also reduces the risk of transmitting the virus from one vaccinated person to another.
The results of another recent study, not yet published, seem to show an even greater advantage for people completely vaccinated 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.
In the United States, a preliminary study released last week by researchers at the Mayo Clinic points to similar benefits for the Modern vaccine. They examined workers at the Mayo Clinic and associated health care centers who had received the first dose of an mRNA vaccine at least 36 days earlier. Compared with 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 in claiming that covid-19 vaccines will reduce transmission, arguing that data were simply not yet available to know for sure. But other experts do he argued that it would be very unusual for an effective vaccine to prevent disease to have no effect on reducing transmission and not useful leaving people worried about an unlikely outcome. In any case, the evidence of these and other studies it should be reassuring for everyone.
Further research will continue to understand the effectiveness of mRNA vaccines 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 coronavirus variants can complicate things, as at least some vaccines have been shown to be less effective against certain variants.
All of this is certainly good news if you hope to end the pandemic as soon as possible. Vaccines that prevent covid-19 disease and transmission will only hinder the spread of coronavirus as more people are vaccinated, and should speed up the time it takes for life to return to normal.