Study shows fourth dose of Pfizer COVID vaccine wanes faster than thirdA study from Israel published today in BMJ shows that the effectiveness of a fourth dose of Pfizer-BioNTech's mRNA COVID vaccine waned faster than a third dose in adults ages 60 and older.The study took place over 10 weeks beginning in January 2022, and compared outcomes of 69,623 adults with three doses of Pfizer with 27,876 adults who received four doses.
The study was conducted when Omicron was the dominant strain in Israel.During the 10 week follow-up period, 106 participants died, including 77 who had a third dose and 23 with a fourth dose.To gauge breakthrough infections, the authors performed a matched analysis that compared positive cases to controls by week since vaccination.
The added relative vaccine effectiveness of a fourth dose against infection quickly decreased over time, peaking during the third week at 65.1% (95% confidence interval [CI], 63.0% to 67.1%) and falling to 22.0% (95% CI, 4.9% to 36.1%) by the end of the 10 week follow-up period, the authors said."This study has shown additional protection of the fourth dose against both SARS-CoV-2 infection and severe covid-19 relative to three doses.
However, the relative vaccine effectiveness against infection varied over time and waned sooner than that of the third dose," the authors said. "By the fifth week after vaccination, relative effectiveness of the fourth dose against SARS-CoV-2 infection dropped back to levels similar to those observed during the first week."May 24 BMJ studyStudy: COVID-19 vaccine protection lower, wanes faster in cancer patientsA UK study suggests that COVID-19 vaccination offers protection against infection, hospitalization, and death for most cancer