A winter COVID-19 surge is in full swing, with the Omicron variant accounting for 95.4% of all cases in the United States.1 In an effort to curb the spread, experts are encouraging people to get their booster shots.
But some people are now testing positive for COVID-19 after getting their boosters.
According to Jacqueline Korpics, MD, medical director for the COVID-19 response for the Cook County Department of Public Health in Illinois, if you test positive for COVID-19 following the booster shot, this means that you have been infected with the virus. You likely do not have a false positive test.
“If your test is positive, vaccinated or not, you should assume you are infected with COVID-19,” Korpics told Verywell.
If you contracted COVID-19 following your booster, this doesn’t mean that the booster is ineffective or doesn’t work. Research shows it may take one or two weeks until the booster is fully effective. Additionally, contracting COVID-19 post-vaccination and post-booster—also known as a breakthrough case—is much more common due to Omicron’s infectious profile, Korpics said.
That’s why it’s more important than ever to get vaccinated with the first, second, and booster dose, she added.
Boosters have been shown to counteract the waning of vaccine-induced protection against the virus.2 One study found that there was an 86% reduction in the odds of testing positive for COVID-19 between 28 and 65 days among people who received a booster compared to those who only received two doses.
“If someone still contracts COVID-19 after being fully vaccinated and boosted, they are much more likely to have an asymptomatic (infection with no symptoms) or mild illness (rather than severe illness or death from COVID-19,” Korpics said.
In addition to boosters, other ways to protect yourself include getting tested, wearing a mask, practicing six-feet social distancing, and maintaining hand hygiene.
Can a COVID-19 Vaccine or Booster Turn a Test Positive?
“The booster shot itself will not make someone test positive,” Matthew P Kronman, MD, MSCE, associate medical director of infection prevention at Seattle Children’s Hospital, told Verywell. “If someone does get COVID after having a booster, they should follow the typical public health recommendations in terms of isolating themself to prevent transmitting the infection to others.”
The Centers for Disease Control and Prevention’s (CDC) most updated quarantine guidance states that if you test positive for COVID-19 you should isolate for 5 days. If you are asymptomatic or your symptoms are resolving (without fever for 24 hours) after those five days, you can leave quarantine but mask when you’re around others for another five days.
“All of their close contacts should quarantine,” Korpics said. “This is the same for any case of COVID-19, whether it is a breakthrough case after vaccination or not.”