That comes as no surprise to a Jim Weisz, of Denton County, who got COVID-19 days after his first shot.
He posted his experience on Facebook, beginning his post with, "I got the vaccine, then I got Covid."
Weisz said he tested positive seven days after his first Pfizer vaccine dose, despite taking safety precautions to keep from getting infected, knowing he was not fully immunized.
"My first thought was like 'how could I have it because I just got the first dose of the vaccine,' and, 'how is this even possible?'" said Weisz.
He said he doesn't know how or where he was exposed.
Doctors say the new variants of the virus may play a role in infection rates among those who've had one or both COVID-19 vaccines.
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The CDC reports 6,000 breakthrough cases. Those are cases in people who've contracted COVID-19 despite being vaccinated.
"The vaccines are not 100% effective and some people will make a greater or lesser immune response to the vaccines, which means they may have more or less protection," said Dallas County Medical Society President Dr. Beth Kassanoff-Piper.
"People that get COVID after a vaccine are less likely to get severely ill and need to be hospitalized or even die from COVID," said Dr. Kassanoff-Piper.
Weisz, who says he's considered high risk, believes the vaccine protected him from what could have been.
"I am thankful for the fact that everything was so minor for me," said Weisz, whose illness lasted only two days.
People are considered fully vaccinated two weeks after they receive their second dose of a two-dose vaccine, such as the Pfizer or Moderna vaccines.