Two doses of BNT162b2 vaccine linked to high short-term protection against infection, which wanes after six months<\/p>\n<\/h3>\n
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TUESDAY, March 1, 2022 (HealthDay News) — Two doses of BNT162b2 vaccine are associated with high short-term protection against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, which wanes after six months, while immunity remains high for those with infection-acquired immunity boosted with vaccination, according to a study published online Feb. 16 in the New England Journal of Medicine<\/em>.<\/p>\n Victoria Hall, from the U.K. Health Security Agency in London, and colleagues examined the duration and effectiveness of immunity in a prospective cohort of asymptomatic health care workers. The time to confirmed infection was compared in vaccinated and unvaccinated persons, stratified by previous infection status.<\/p>\n Overall, 27 percent of the 35,768 participants had a previous SARS-CoV-2 infection. The researchers found that vaccine coverage was high; 97 percent had received two doses (78 percent BNT162b2 with a long interval between doses; 9 percent BNT162b2 with a short interval; 8 percent ChAdOx1 nCoV-19 vaccine). A total of 2,747 primary infections and 210 reinfections were observed between Dec. 7, 2020, and Sept. 21, 2021. For previously uninfected participants who received BNT162b2 vaccines with a long interval, the adjusted vaccine effectiveness decreased from 85 to 51 percent at a median of 14 to 73 days and a median of 201 days, respectively, after the second dose; no significant difference was seen for those receiving BNT162b2 with a long or short interval. The adjusted vaccine effectiveness at 14 to 73 days after the second dose was 58 percent among ChAdOx1 nCoV-19 vaccine recipients. In unvaccinated participants, infection-acquired immunity waned after one year; in those who were subsequently vaccinated, even those infected more than 18 months previously, immunity remained consistently higher than 90 percent.<\/p>\n “The highest and most durable protection was observed in participants who received one or two doses of vaccine after a primary infection,” the authors write.<\/p>\n One author disclosed financial ties to the pharmaceutical industry.<\/p>\n