Study shows fourth dose of Pfizer COVID vaccine wanes faster than third
A 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 study
Study: COVID-19 vaccine protection lower, wanes faster in cancer patients
A UK study suggests that COVID-19 vaccination offers protection against infection, hospitalization, and death for most cancer patients but is less effective and wanes faster than in the general population.
In the study, published yesterday in The Lancet Oncology, a team led by University of Oxford researchers mined public data on English adults with and without cancer who had received two doses of a COVID-19 vaccine from Dec 8, 2020, to Oct 15, 2021, a period during which the Delta variant became dominant.
Among the 377,194 patients with active or recent cancer, 42,882 (11.4%) tested positive for COVID-19, compared with 5,748,708 of 28,010,955 (20.5%) controls without cancer. Estimated initial vaccine effectiveness (VE) was 65.5% (95% confidence interval [CI], 65.1% to 65.9%) among cancer patients and 69.8% (95% CI, 69.8% to 69.9%) among controls.
By 3 to 6 months, however, the difference in VE had widened, at 47.0% (95% CI, 46.3% to 47.6%) among cancer patients and 61.4% (95% CI, 61.4% to 61.5%) among controls. The COVID-19 vaccine offered more protection against hospitalization (83.3%) and death (93.4%) than against infection in cancer patients but also waned after 3 to 6 months.
Relative to controls, VE was much lower among patients with the blood cancers leukemia or lymphoma, a recent cancer diagnosis, or chemotherapy or radiotherapy within the past year.
"This highlights the importance of vaccination booster programmes and rapid access to COVID-19 treatments for people undergoing cancer treatments," senior author Peter Johnson, MD, of the University of Southampton, said in a University of Oxford news release.
In a related commentary, Nicole Kuderer, MD, of the Advanced Cancer Research Group, and Gary Lyman, MD, MPH, of the Fred Hutchinson Cancer Research Center, both of Seattle, said the results illustrate the importance of prioritizing cancer patients for additional vaccine doses, treatments, and preventive therapies.
"In the meantime, high-quality face masks and physical distancing offer important protection against any strain of SARS-CoV-2," they wrote.
May 23 Lancet Oncol study and commentary
May 23 University of Oxford news release