- The researchers analyzed more than 11,000 hospital admissions and emergency department visits to see how effective COVID-19 vaccines are in preventing illness.
- They found that all three doses of the Pfizer mRNA COVID-19 vaccine are highly effective in initially preventing hospitalizations.
- While that high level of effectiveness is waning, experts say vaccines still provide key protection against COVID-19.
“Pfizer BioNTech COVID-19 booster doses significantly improve protection against Omicron, although that protection appears to wane after 3 months against emergency room visits and even for hospitalization,” lead author Sara Y. Tartof , PhD, research scientist and infectious disease specialist. the epidemiologist at the Department of Research and Evaluation at Kaiser Permanente Southern California said in a statement.
The researchers analyzed more than 11,000 hospital admissions and emergency department visits that did not result in hospitalization for acute respiratory infection.
They focused on Kaiser Permanente patient records in Southern California from December 1, 2021, through February 6, 2022, when the Delta and Omicron variants were circulating. That time period was also the peak of the Omicron wave in California.
According to the researchers, after two doses of the vaccine, the effectiveness of the Omicron vaccine was 41 percent against hospital admission and 31 percent against emergency department visits at nine months.
They found that a booster shot of the Pfizer vaccine provided about 80 to 90 percent protection against serious outcomes caused by Delta and Omicron immediately after administration.
But the effectiveness against Omicron-related hospitalization began to wane at around three months.
The vaccine prevented hospitalization within three months of administration by 85 percent. But the effectiveness dropped to 55 percent after the three-month mark.
They also looked at the efficacy of the vaccine in preventing Omicron-related emergency department visits that did not result in hospitalization. They found that three doses of the Pfizer vaccine were 77 percent effective within three months of administration. It dropped to 53 percent after the three-month mark.
“Although Pfizer COVID-19 protection levels against omicron after 3 doses are substantially higher than those observed after 2 doses, they are lower than those observed for delta or other strains of COVID-19,” Tartof said in a statement. .
It warned that additional doses of “current, adapted or novel COVID-19 vaccines” might be needed to maintain high levels of protection against new waves of infection caused by Omicron or future variants with similar potential to escape protection.
Experts stress that COVID-19 vaccines are a vital part of ending the pandemic, and even if their effectiveness declines, they provide key and important protection against serious illness.
“One of the misunderstandings that people have about the COVID vaccine, and there are a lot of reasons why they’re confused: They think if you’re vaccinated, you won’t get the virus,” said Peter Pitts, former FDA associate commissioner and chairman of the Public Interest Medicine Center.
While that’s true for many people, he explained, the vaccine doesn’t provide complete protection against infection.
“Especially when we have a mutation that is highly infectious,” Pitts said. “That [vaccination] mitigates the symptoms.”
He added that with currently available vaccines, mitigation of severe symptoms and hospitalizations is “extremely robust, as evidenced by high infections and low hospitalizations.”
“The reality is that vaccines, as they currently exist, are extremely effective in fulfilling their mission of keeping people out of the hospital and dying,” Pitts confirmed.
Pitts said the effectiveness of the vaccine is expected to decline over time. This may be due in part to decreased antibodies, but this study did not measure antibody levels.
Pitts explained that this research tested the hypothesis that vaccine protection declines over time, with the vaccine providing greater protection against some variants than others.
“But it’s still effective,” he said. “It’s not necessarily less effective.”
He compared it to needing $20 to buy an item when you already have $40.
“And then the price goes up to $25; you still have enough money to pay for it,” Pitts said. “So the big question is; What is robust enough?
“This study does not answer that question,” he continued. “Because we don’t necessarily know how to properly create those studies.”
Robert G. Lahita, MD, PhD, Director of the Institute for Autoimmune and Rheumatic Diseases at Saint Joseph Health and author of Immunity St. explained that vaccines decline over time. He suspects that COVID vaccination may be required annually, like the flu shot.
“This is not an unexpected problem considering the nature of the virus,” Lahitahe told Healthline.
He noted that although different from COVID-19, some common human coronaviruses are related to the common cold, which people can catch frequently. So he’s not surprised that vaccine-induced immunity can be short-lived. But he noted that the vaccines have been effective enough that hospitalizations are down across the country.
“I would say that future research will show that the vaccine lasts differently for different people”, “This would depend on age, lifestyle, general health, etc.
He also noted that the vaccine’s efficacy of 53 percent at three months or more is similar to the protection a flu shot might provide.
New research finds that the efficacy of Pfizer’s COVID vaccine was initially powerful, but dropped significantly after three months during the height of the Omicron wave.
Experts say it’s not unusual for vaccine effectiveness to decline over time and that vaccines are significantly protective in preventing serious illness for many people.