Coronavirus vaccine protection was much weaker against omicron, data shows

While coronavirus shots still provided protection during the omicron wave, the shield of coverage they offered was weaker than during other surges, according to new data from the Centers for Disease Control and Prevention. The change resulted in much higher rates of infection, hospitalization and death for fully vaccinated adults and even for people who had received boosters.

Cases by vaccination status

The spike of cases in the delta and omicron waves greatly reduced the difference in rates between the vaccinated and unvaccinated.
Fully vaccinatedUnvaccinatedUnvaccinatedBoostedAbout 3x as high5x as highduring omicron waveduring delta wave

The decline in protection continued a pattern driven by coronavirus vaccines’ reduced effectiveness over time, combined with the increasing contagiousness of the delta and omicron waves.

Before delta struck the United States in July, there were five to 10 cases of covid-19 for every 100,000 fully vaccinated adults each week, while the rate for unvaccinated people was 50 to 90 cases.

In the delta wave, unvaccinated people were five times as likely to get infected as vaccinated people. With omicron, that difference dropped to less than three times as likely.

Vaccine effectiveness over time by variant

Delta

Fully vaccinatedMonths since last dose

Omicron

Fully vaccinatedBoosted

Omicron caused unprecedented hospitalization along with infections.

The new data shows that vaccines provided greater protection against hospitalization than for infection during the omicron wave, even as that protection waned. Before omicron, unvaccinated people were 15 times as likely to be hospitalized as were fully vaccinated people. With the latest coronavirus variant, the difference in rates dropped to about seven times as much.

Hospitalizations in adults by vaccination status

The difference in hospitalization rates between the unvaccinated and vaccinated was cut in half as omicron became predominant.
per 100,000Fully vaccinatedUnvaccinatedUnvaccinated7x as high15x as highduring omicron waveduring delta wave

Among the most vulnerable people — those 65 or older — the unvaccinated were about four times as likely to be hospitalized as fully vaccinated people who also had boosters. Before omicron, the difference was more than nine times.

Younger unvaccinated people were about five times as likely to be hospitalized as their peers with boosters.

Vaccines provided their greatest protection against death. CDC’s data on deaths went through only December, before the peak of more than 2,600 deaths per day in January. At the end of December, unvaccinated people were 10 times as likely to die as the vaccinated who had received the initial series of two Pfizer-BioNTech or Moderna shots, or a single dose of the Johnson & Johnson vaccine. That difference was about one-third smaller than it had been before omicron.

Deaths in adults by vaccination status

The difference in death rates between the vaccinated and unvaccinated was about the same during omicron as during delta. Boosters provided much more protection, but the difference in death rates between the unvaccinated and boosted fell by almost half in December.
per 100,000Fully vaccinatedUnvaccinatedUnvaccinatedUnvaccinatedBoostedabout 10x as high15x as highabout 12x as highduring omicron waveduring delta wavebefore omicron wave

Before omicron, unvaccinated people were 50 to 60 times as likely to die as people who had received the initial series of vaccines and a booster. That difference dropped in late December to 27 times as high.

The breakthrough estimates are drawn from a sample of health departments that track vaccine status for infected people.