You’re vaccinated for COVID-19, and you just tested positive. Now what?

"I thought it was typical springtime allergies in New England,” said Kevin, 42, who spoke on the condition that his last name not be used. The symptoms worsened to headaches, body aches and sleepless nights. His doctor told him that it might be the flu but suggested a coronavirus test. The result was positive.

“You don’t think it will be you,” said Kevin, who isolated in his Provincetown townhome for 10 days.

“At the end of the day, the vaccination still worked,” he said. “I didn’t get as sick as people who got COVID prior to the vaccination being available.”

‘Breakthrough’ cases are rare.

If you’re one of the small number of fully vaccinated people who later test positive for COVID-19, what should you do?

COVID vaccines have been highly effective in preventing COVID-19, especially hospitalisation and death, and are generally working as expected, doctors say. The vaccines also reduce the risk of spreading the virus.

Although the risk of vaccinated people becoming infected with the virus is low, it can still happen, experts said.

“Yes, this will happen, unusual but will happen," said Dr Sandro Galea, dean of the Boston University School of Public Health.

Those rare cases are called breakthrough infections and as of April 30, there were more than 10,000 of these infections reported from 46 American states and territories, according to the Centres for Disease Control and Prevention. The CDC has stopped recording such infections if there are no severe symptoms, so the number for cases, including mild ones, is most likely higher.

What to do if it happens to you?

A fully vaccinated person who experiences symptoms consistent with COVID-19 should isolate themselves from others, the CDC said.

“Broadly, someone who tests positive should isolate for 10 days,” Galea, noting CDC guidelines, said.

Dr Eric Cioe-Peña, director of Global Health at Northwell Health in New Hyde Park in New York, said the guidelines were not much different from those for someone who tested positive before the vaccines were available.