Research conducted 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 the effectiveness of a vaccine in Americans, found that the vaccine’s ability to protect against infection stood at 88% in its first month, then fell to 47% after just five months.
But even as the Delta variant became the predominant strain across the Southland, the vaccine’s effectiveness at preventing COVID-19 hospitalizations held steady at close to 90% for as long as six months. What’s more, it maintained that power across vaccine recipients of all age groups.
The study, funded by Pfizer and published Monday in the journal Lancet, also provides strong new evidence that the waning immunity against infection probably would have been seen with or without the arrival of the Delta variant.