Vaccines can be great at preventing you from getting sick, while at the same time not necessarily stopping you from getting infected or spreading the germ. Preliminary evidence seems to suggest the COVID-19 vaccines make it less likely someone who’s vaccinated will transmit the coronavirus, but the proof is not yet ironclad. Unvaccinated people should still be diligent about mask-wearing, physical distancing and other precautions against the coronavirus.

Anthony Fauci, chief medical adviser to President Biden, said the new guideline is “based on the evolution of the science” and “serves as an incentive” for the almost two-thirds of Americans who are not yet fully vaccinated to go ahead and get the shot.

But some people cannot be vaccinated because of underlying conditions. Others with weakened immune systems, from cancer or medical treatments, may not be fully protected by their vaccinations. Children aged 12 to 15 became eligible for the Pfizer-BioNTech vaccine only on May 10, 2021. And no COVID-19 vaccines are yet authorized for the nearly 50 million children in the U.S. younger than 12.

As restrictions are lifted and people start to leave their masks at home, some people worry: Can you catch COVID-19 from someone who’s vaccinated?

Vaccines don’t always prevent infection

Researchers had hoped to design safe COVID-19 vaccines that would prevent at least half of the people vaccinated from getting COVID-19 symptoms.

Fortunately, the vaccines have vastly outperformed expectations. For example, in 6.5 million residents of Israel, aged 16 years and older, the Pfizer–BioNTech mRNA COVID-19 vaccine was found to be 95.3% effective after both shots. Within two months, among the 4.7 million fully vaccinated, the detectable infections fell by 30-fold. Similarly in California and Texas, only 0.05% of fully vaccinated health care workers tested positive for COVID-19….