Vaccines work well in reducing transmission of coronavirus: Health Institute

The coronavirus vaccines are very effective in reducing the transmission of the coornavirus, scientists at public health institute RIVM discovered in a study that will be published on Thursday, NOS reports. An important note is that the study was done when the Alpha variant of the coronavirus was dominant in the Netherlands. But the researchers believe their findings apply to the more contagious Delta variant to some extent as well.

This study was done between February and May. The researchers looked at how often vaccinated people transmitted the coronavirus to people in their own household, and compared that to how often unvaccinated people did. The data set contained over 113 thousand infectious persons and over 250 thousand documented contacts with housemates. Of the group of infectious people, 662 were fully vaccinated and over 2 thousand were partially vaccinated.

Fully vaccinated people who became infected with the virus infected 11 percent of their housemates. Unvaccianted individuals who became infected, transmitted SARS-CoV-2 to 31 percent of their housemates. Adjusted for age, vaccination status of the housemates, and the month of the year, the scientists concluded that the chance of being infected by a fully vaccinated person within a household is 71 percent smaller than by an unvaccinated person. Vaccinated housemates were also 75 percent less likely to become infected.

After partial vaccination, infected people still transmitted the virus to 29 percent of their housemates. One shot of a vaccine that requires two therefore hardly protects against transmission of the virus.

"It will probably look a bit different with the Delta variant," lead researcher Brechje de Gier said to NOS. "But we cannot make firm statements based on this data. This study shows that the vaccinations work very well against transmission of the virus and that has been clearly proven for the first time." She added that the data also shows how important it is to be fully vaccinated. "To protect yourself and to protect those around you."

It was already known that full vaccination protects well against contracting SARS-CoV-2 and against serious illness, hospitalization, and death.