Analysis of hospital workers suggest COVID-19 vaccines are preventing coronavirus infections

The COVID-19 vaccines being administered in the U.S. were authorized for use because they dramatically reduced the risk of getting the disease when tested in clinical trials. However, those trials didn’t test the vaccines’ ability to prevent infection with the SARS-CoV-2 virus that causes COVID-19 — the first step on the road to developing the disease itself.

Scientists suspect the vaccines do thwart infections to some extent. Two new studies bolster their case.

Both studies compare coronavirus infection rates among vaccinated and unvaccinated people who work at a single medical center. And in both cases, being vaccinated was indeed associated with a significantly lower risk of testing positive for an infection.

Hospital employees make good study subjects because they were among the very first people to get access to COVID-19 vaccines. That means they have a longer track record to mine when it comes to assessing the performance of the shots.

Another upside: Many hospitals routinely screen their workers for coronavirus infections. That makes it possible to identify people who seem perfectly healthy but harbor the SARS-CoV-2 virus in their system — and have the potential to spread it to others.

Unlike in a clinical trial, the hospital workers in these two studies decided for themselves whether to get the COVID-19 vaccine or not. There was nothing random about it.

That means that if coronavirus infection rates are different for vaccinated and unvaccinated workers, it might be due to factors other than the vaccine itself. Perhaps the people who made a point of getting the shots were also more likely to wear face masks, wash their hands thoroughly, or take other actions to avoid getting sick.