Health experts say it's possible for some people to get infected with COVID-19 even if they're fully vaccinated, but it's still important to get the shot.Experts say it takes two weeks after a person's final shot to build full immunity to COVID-19. But none of the vaccines are 100% effective at preventing infection, so some people will still contract the virus. But they won't get as sick and likely won't transmit it as easily.When Pfizer was testing its vaccine in the fall, Dr. Amy Aobota volunteered. Two months later, she got a runny nose and then a positive COVID-19 test."A lot of people I know were kind of freaked out by that, saying, 'How can you test positive if you were vaccinated?'" she said.But her response was, the vaccine worked."If the vaccine turns the virus into no more than the common cold, that's a huge success," she said.Experts agreed. "We do know based on evidence that vaccines are really effective at preventing severe disease," said. Dr. Jose Mercado, of Dartmouth-Hitchcock Medical Center in New Hampshire.Mercado said Sobota is among a small percentage of people who get infected after being vaccinated. But he said they're still more protected from the vaccine."Immunity from the vaccine is more robust than immunity from natural infections," he said.The message is to continue masking and mitigation strategies and to get vaccinated."I've had friends who've been in the hospital, who've had symptoms for weeks or even months after being sick who weren't vaccinated, and if we can prevent that with a vaccine, that's a huge success," Sobota said.Preliminary research shows vaccines might also reduce the spread of the virus."It should reduce the amount of virus that you have in your body," Mercado said. "It should reduce the amount that you can transmit."