Three months after the United States’ Covid-19 vaccination campaign began, researchers are starting to collect data showing that the vaccines are just as good in the real world as they were in the clinical trials testing them.

Recent studies have consistently shown that the vaccines don’t just protect against symptoms — they reduce the risk that someone will get infected with the coronavirus, a signal that they’ll reduce the spread of the virus, not just prevent sickness.

The Moderna and Pfizer/BioNTech vaccines were both around 95 per cent effective at protecting people against symptomatic Covid-19 in large trials.

It was never guaranteed that they’d perform just as well when they were distributed to the general public.

Despite the best efforts of researchers to closely mimic the real world in a clinical trial, they’re never quite the same. The types of people who volunteer for trials sometimes aren’t representative of the general population.

Certain groups, like pregnant people, weren’t recruited for the trials. The dose administration was in a more controlled environment than mass vaccination sites.

That’s why it’s so encouraging to see these vaccines do just as good a job protecting people outside of the clinical trials.

This week, the Centers for Disease Control and Prevention announced encouraging results from a study designed to check how well the Covid-19 vaccines could protect frontline workers against infections in a real-world setting.

Just under 4,000 health care workers and first responders swabbed themselves weekly over 13 weeks to check for the virus. In that group, which is regularly exposed to Covid-19 at work, two shots of the vaccines were 90 percent effective against infection. A single dose was also protective; it prevented 80 percent of infections.

The CDC’s results build on other research that has had similarly good findings.

The first real-world data on vaccines came from Israel, which had a fast start to its Covid-19 vaccination program. One study from February compared around 600,000 people who had been vaccinated with the Pfizer / BioNTech shots to 600,000 people who had not been vaccinated.

It found that it was 94 percent effective against symptomatic Covid-19 a week after the second dose.

In the United States, the first data came from people living in long-term care facilities and health care workers — who also happened to be the first people to get the vaccine in the US.

A close look at the long-term care facilities was especially important for researchers because the people living in them are elderly and very vulnerable to Covid-19.

In addition, vaccines sometimes don’t work as well in older adults. So it was good news to see that just one dose of the Pfizer / BioNTech vaccine was 63 percent effective against infection — not just symptoms — of the coronavirus in two long-term care facilities in Connecticut, according to a CDC report from March. 

Another study found that the shots were also 88 percent effective against coronavirus infections in a group of Mayo Clinic patients vaccinated between December 2020 and early February 2021, presumably all long-term care facility residents and health care workers.

As vaccination campaigns around the world continue, researchers will keep collecting data and tracking their effectiveness in different groups.

There are still unanswered questions — experts still want to know how the available vaccines compare to each other, how long protection lasts, and how well they work in people who are immunocompromised, for example.

But the studies we have so far are early signals that the Covid-19 vaccines are working, and working extremely well.

That makes holding off the looming fourth coronavirus surge in the United States even more important: the more people stay safe now, the more get the benefit of the lifesaving shots.