In a huge Qatar study of 907k, Pfizer effectiveness against infection fell to only 20% in months five to seven after the second dose, which is admittedly pretty shocking (but don't get distracted by the shiny object -- boosters!):
The results indicated that vaccine effectiveness against any SARS-CoV-2 infection was 36.8% (95% CI, 33.2-40.2) in the third week after the first dose, peaking at 77.5% (95% CI, 76.4-78.6) in the first month following the second dose. Effectiveness gradually waned thereafter, then dropped after the fourth month to reach about 20% in the fifth through seventh months, according to the researchers.
“These findings suggest that a large proportion of the vaccinated population could lose its protection against infection in the coming months, perhaps increasing the potential for new epidemic waves,” Chemaitelly and colleagues wrote.
More.
But these claims fly in the face of the Provincetown incident of July 4th, where there was mass infection among fully vaccinated individuals, a plurality of whom had received Pfizer. Loss of protection against infection appears to be coterminous with vaccination "protection", not something which occurs after month seven, for example. The median interval from completion of vaccination to symptom onset in that incident was 3 months, which means half of the infected symptomatic cohort had been recently vaccinated (6-86 days!):
Among fully vaccinated symptomatic persons, the median interval from
completion of ≥14 days after the final vaccine dose to symptom onset was
86 days (range = 6–178 days).
