Pfizer Vaccine Protection Wanes After 6 Months Study Finds July 28, 2021 – Pfizer’s COVID-19 vaccine continues to show strong protection against serious illness and hospitalization after 6 months, but overall protection against the virus appears to wane after a half a year, according to a new study. The July 28, 2021, pre-print report of the study, which has not been peer-reviewed, suggests a gradual "declining trend in vaccine efficacy" over 6 months after two doses of the Pfizer vaccine in more than 45,000 people worldwide. The study finds overall effectiveness falls from 96% to 84%. At the same time, a third booster dose of the Pfizer vaccine increases neutralizing antibody levels against the Delta variant by more than 5 times, compared to levels after just a second dose in people ages 18 to 55 years old, new data from Pfizer shows.