During the omicron surge and the delta wave before it, COVID-19 vaccines were most likely to keep adults out of American hospitals when they had received three doses, according to new information released Friday by the U.S. Centers for Disease Control and Prevention.
Three studies, one published by the Journal of American Medicine, underscored the importance of booster shots as case numbers reach record levels in Michigan, hospitalizations remain high and the highly contagious strain has been found in most state counties.
With the omicron variant, vaccines were found to be 90% effective at preventing hospitalization and 82% effective at preventing emergency department and urgent care visits when patients had received two doses of either the Pfizer or Moderna vaccines and booster shots, found one multistate study. This was down from 94% with delta, according to the analysis, which looked at emergency department and urgent care and hospitalizations from August to Jan. 5. Among those seeking care, a median interval of 44 days had passed since the third dose.
With delta, the vaccines were about 81% effective at keeping people out of hospitals within six or more months after the second dose. With omicron, this fell to 57%.
Added benefits of booster doses were especially prominent among people 50 to 64 and those 65 and older, a second study looking at data from April to late December found.
Rates of COVID-19 cases per 100,000 people were lowest among fully vaccinated people with booster doses (149) compared to fully vaccinated people without a booster dose (255), and much lower than rates among unvaccinated people (726) in December, as omicron was emerging, according to the study, examining information from 25 U.S. jurisdictions.
This is consistent with recent information from some Michigan health systems, reporting 85 to 95% of patients with COVID-19 have not had booster shots.
About 95% of vaccinated patients with COVID-19 admitted to Southfield-based Beaumont Health’s eight hospitals have not received booster shots, Dr. Matthew Sims, director of infectious disease research, said Friday.
Meanwhile, the percentage of unvaccinated patients has decreased to about 55 to 65% of those hospitalized and isolated with COVID-19, he said. These numbers were higher during the long fall and winter surge dominated by the delta variant.
The rate increases among those who are sick enough to require critical care or intubation. “But not as much as it used to,” Sims said.
Of those boosted patients, he could not say how many were admitted because they have COVID or because they tested positive upon arrival for treatment related to, for example, a vehicle crash or appendicitis. “It could be that most of them are there for completely other reasons,” he said.
In Michigan, about 47% of people who are fully vaccinated have gotten booster shots. However, some, depending on when they received their shots, might not be eligible for the additional doses. About 58% of residents 5 and older have received all their primary shots, according to Michigan Department of Health and Human Services data.
Doctors have been stressing the importance of third shots especially since omicron has overtaken the delta variant in Michigan.
The U.S. Centers for Disease Control and Prevention now recommend everyone 12 and older should get third doses of the mRNA vaccines, Pfizer and Moderna.
This guidance has changed in the last several months. Before omicron, only those at greater risk of severe outcomes were told they should receive booster shots.
The CDC has also shortened the interval between second and third doses from six months to five for both mRNA vaccines. (Those who received a single Johnson & Johnson shot should receive an mRNA dose at least two months later.)
RELATED: CDC now says everyone 12 and older should receive mRNA booster shot
Those who are vaccinated and still find themselves in hospitals with COVID tend to have a lot of other medical issues, such as cancer, chronic pulmonary disease, chronic heart disease or obesity, doctors have said. Their age and other factors might also put them at greater risk.
The omicron surge, arriving before the delta swell significantly subsided and as hospitals were already overwhelmed and short-staffed, is proving to cause less severe illness. Fewer patients are in intensive care or on ventilators.
However, even if omicron is half as bad as delta, the sheer number of infections are bringing large numbers of people to hospitals. “Yes, it’s not as dangerous, it’s not as bad, but there is so much more of it that we are still getting a lot of very sick people,” Sims said.
Those who are vaccinated and hospitalized have not typically been recently vaccinated. They are months out from their primary doses, Sims said.
Though two shots of the mRNA vaccine and one dose of the Johnson & Johnson vaccine qualify residents as “fully vaccinated,” the CDC is stressing people should remain “up to date” on vaccines, meaning they have received all recommended doses.
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