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Research in Southern California has confirmed the dramatic erosion of the Pfizer-BioNTech COVID-19 vaccine’s protection against “breakthrough” coronavirus infections.
The new study, one of the largest and longest to track a vaccine’s effectiveness in Americans, found that the vaccine’s ability to protect against infection was 88% in its first month , then fell to 47% after just five months.
But even though the Delta variant has become the predominant strain in Southland, the vaccine’s effectiveness in preventing COVID-19-related hospitalizations has remained stable at nearly 90% for six months. In addition, he maintained this power among vaccinees of all age groups.
The study, funded by Pfizer and published Monday in the journal Lancet, also provides strong new evidence that the decline in immunity to infection would likely have been observed with or without the arrival of the Delta variant.
The researchers, led by infectious disease epidemiologist Sara Tartof of Kaiser Permanente Southern California, relied on several findings to conclude that the Delta variant was not the determining factor in the decreased effectiveness of the vaccine against infection. Instead, the passage of time seemed to be the key to the resurgent vulnerability of a vaccinated person.
To begin with, Tartof and his colleagues found that re-inoculation with the Pfizer-BioNTech vaccine protected against infection with the Delta variant as well as against infection with other versions of the coronavirus.
Second, the vaccine’s ability to keep vaccinated people out of the hospital remained high for a period of time as the Delta variant gained traction in Southern California.
And third, the breakthrough infections were more closely related to the time that had passed since vaccination than they were to the particular viral variant involved.
By showing that the decline in immunity, not the Delta variant, was the likely reason for the increase in peak infections, the study suggests that there may not be a need to reformulate a Pfizer booster. BioNTech which specifically targets Delta. For now, at least, a third injection identical to the first two would likely extend the vaccine’s record of early protection against all strains, including Delta, Tartof said.
The Southern California research searched the medical records of 3,436,957 patients aged 12 and older who were enrolled in the Kaiser Permanente Southern California healthcare system between mid-December and early August. Almost 2.3 million of them were not vaccinated during this period, while just over one million received two doses of the Pfizer-BioNTech vaccine, now known as Comirnaty.
Rates of SARS-CoV-2 infection, as well as hospitalization for COVID-19, were tallied for both patient groups and compared for six months.
The protection Comirnaty provides beyond six months has been an open question, raised only by Israeli studies that suggest COVID-19 hospitalization rates are increasing in people over 60.
In another recent study, researchers at Emory University and Stanford found that six months after being inoculated with Comirnaty, about half of 56 young and middle-aged adults had no detectable neutralizing antibodies against the virus. SARS-CoV-2. The reduced immunity was particularly dramatic against the Delta, Beta, and Mu coronavirus variants.
This study was posted last week on BioRXiv, a site where researchers share preliminary work before it is peer reviewed. But its findings on “a substantial decrease in antibody responses” – as well as a decrease in immunity provided by T cells – suggest that a third booster vaccination “may be warranted,” its authors wrote.
The Lancet study reflects a very large and diverse population of Californians who are still being followed. As such, it’s poised to offer U.S. policymakers insight into who needs boosters most, and when.
“We really have to watch it closely to make sure we catch it quickly if that happens,” Tartof said in an interview.
She said the Kaiser Permanente team, working with Pfizer, continues to analyze their data on a weekly basis. The team is ready to alert public health officials if hospitalizations start to increase in a segment of the population, she added.
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