Why are so many vaccinated people getting COVID-19 lately?
A couple of factors are at play, starting with the emergence of the highly contagious omicron variant. Omicron is more likely to infect people, even if it doesn't make them very sick, and its surge coincided with the holiday travel season in many places.
People might mistakenly think the COVID-19 vaccines will completely block infection, but the shots are mainly designed to prevent severe illness, says Louis Mansky, a virus researcher at the University of Minnesota.
And the vaccines are still doing their job on that front, particularly for people who've gotten boosters.
Two doses of the Pfizer-BioNTech or Moderna vaccines or one dose of the Johnson & Johnson vaccine still offer strong protection against serious illness from omicron. While those initial doses aren’t very good at blocking omicron infection, boosters — particularly with the Pfizer and Moderna vaccines — rev up levels of the antibodies to help fend off infection.
Omicron appears to replicate much more efficiently than previous variants. And if infected people have high virus loads, there's a greater likelihood they'll pass it on to others, especially the unvaccinated. Vaccinated people who get the virus are more likely to have mild symptoms, if any, since the shots trigger multiple defenses in your immune system, making it much more difficult for omicron to slip past them all.
Advice for staying safe hasn't changed. Doctors say to wear masks indoors, avoid crowds and get vaccinated and boosted. Even though the shots won’t always keep you from catching the virus, they'll make it much more likely you stay alive and out of the hospital.
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The omicron variant accounted for 95% of new coronavirus infections last week, according to U.S. health officials’ latest estimates.
The Centers for Disease Control and Prevention posted its newest estimates Tuesday. The CDC uses genomic surveillance data to make projections about which versions of the COVID-19 viruses are causing the most new infections.
The latest estimates suggest a dramatic swing — in just one month — in which version of the coronavirus is most abundant. Beginning in late June, the delta variant was the main version causing U.S. infections. The CDC said more than 99.5% of coronaviruses were delta as recently as the end of November.
The CDC’s estimates are based on coronavirus specimens collected each week through university and commercial laboratories and state and local health departments. Scientists analyze their genetic sequences to determine which versions of the COVID-19 viruses are most abundant.
However, those specimens represent just a small fraction of what’s out there. More than 2.2 million cases were reported in the last week in the U.S. The CDC has been revising estimates for past weeks as it gets more data.