New data from Israel, which had the fastest Covid-19 vaccine rollout in the world, provides real evidence that widespread vaccination against the coronavirus can protect unvaccinated people as well.
The Israeli study, published Thursday in the journal Nature Medicine, took advantage of the fact that until recently Israel only vaccinated people aged 16 and over. For every 20 percentage point increase in the proportion of 16 to 50-year-olds who were vaccinated in a community, the proportion of unvaccinated under 16-year-olds who tested positive for the virus fell by half.
“Vaccination not only benefits the individual vaccinated, but also the people around them,” said Roy Kishony, a biologist, physicist and data scientist who studies microbial evolution and disease at the Technion-Israel Institute of Technology. Dr. Kishony led the research with Dr. Tal Patalon, who heads KSM, the Maccabi Research and Innovation Center, in Israel. The first authors of the paper are Oren Milman and Idan Yelin, researchers in Dr. Kishony’s laboratory.
Israel began vaccinating adults in December last year. Within nine weeks, it had vaccinated nearly half of its population.
The researchers examined the anonymized electronic health records of members of Maccabi Healthcare Services, an Israeli HMO. They analyzed vaccination reports and virus test results between December 6, 2020 and March 9, 2021. The records were from 177 different geographic areas with different vaccination rates and vaccination rates.
For each municipality, they calculated the proportion of adults between the ages of 16 and 50 who were vaccinated at different times. They also calculated the percentage of children under the age of 16 who tested positive for PCR.
They found a clear connection: As more and more adults in a community were getting vaccinated, the proportion of children who tested positive for the virus decreased as a result.
People who are vaccinated are significantly less likely to contract the virus. Research also suggests that even if people who have been vaccinated become infected with the virus, they may have lower viral loads, which reduces their infectivity. As more and more people are vaccinated, the likelihood that unvaccinated people will encounter infected, contagious people is decreasing.
“The results are consistent with the fact that vaccinated people not only do not get sick themselves, but also do not transmit the virus to others,” said Dr. Kishony. “Such effects can be intensified over several infection cycles.”
In another recent article that has not yet been published in a scientific journal, Finnish researchers reported that after vaccination by health workers, even unvaccinated family members were less likely to be infected with the virus.