How long does COVID vaccine immunity last?
Updates on vaccine research
by Pinedale Online!
November 2, 2021
Protection, immune response fall after Pfizer COVID vaccine, data show
CIDRAP-Center for Infectious Disease Research, University of Minnesota, October 7, 2021
Two new large, real-world studies in the New England Journal of Medicine (NEJM) show waning Pfizer/BioNTech COVID-19 vaccine protection, one finding dramatically lower protection against infection—but not hospitalization or death—5 to 7 months after the second dose in Qatar, and the other detailing reduced immune response over 6 months in Israel. Protection drops to 20% after 5 to 7 months according to a team led by Cornell University at Qatar researchers.
Waning Immunity after the BNT162b2 Vaccine in Israel
The New England Journal of Medicine, www.nejm.org, October 22, 2021
These findings indicate that immunity against the delta variant of SARS-CoV-2 waned in all age groups a few months after receipt of the second dose of vaccine. The success of the vaccination policy is challenged by breakthrough infection and disease in fully vaccinated persons. One potential cause of breakthrough infection is the emergence of new variants of concern that escape immunity, thus reducing the effectiveness of the vaccine. The rate of confirmed SARS-CoV-2 infection showed a clear increase as a function of time from vaccination. The appearance and rapid predominance of the delta variant in June 2021 resulted in a dramatic increase in the number of new SARS-CoV-2 infections among fully vaccinated persons, which aroused concern regarding decreased efficacy of the vaccine over time. The rate of severe Covid-19 cases also increased as a function of time from vaccination.
New study: Nursing home residents, health care workers lose more than 80% of their COVID-19 immunity six months after Pfizer vaccine
Case Western Reserve University, Cleveland, Ohio, www.thedaily.case.edu, September 14, 2021
A new, multi-institutional study led by Case Western Reserve University—in partnership with Brown University—found that COVID-19 antibodies produced by the Pfizer vaccine decreased sharply in senior nursing home residents and their caregivers six months after receiving their second shots. The researchers, including a lab team at Harvard University, found that individuals’ antibody levels decreased more than 80% after six months; the results were the same in seniors (median age 76) and caregivers (median age 48) and old alike, according to the study. The sharp decline is particularly problematic for the seniors, because earlier research found that within two weeks of receiving the second dose of vaccine and being considered "fully vaccinated," seniors who had not previously contracted COVID-19 already showed a reduced response in antibodies that was substantially lower than the younger caregivers experienced. By six months after vaccination, the blood of 70% of these nursing home residents had "very poor ability to neutralize the coronavirus infection in laboratory experiments".
Here’s Who May Need a Fourth COVID-19 Vaccine Dose
The CDC has found reduced vaccine effectiveness in people who are immunocompromised compared with people who are not. It now advises that certain people who are immunocompromised can get a fourth vaccine dose. One reason for these new guidelines is that vaccine efficacy has been shown to drop over time, placing certain groups at increased risk.
Efficacy and protection
National Institute for Public Health and the Environment, Netherlands Ministry of Health, Welfare and Sport, October 14, 2021
After the first vaccination, you may still get COVID-19 because your immunity to the virus is not yet fully developed. After the second vaccination, there is a much lower risk of becoming ill, because you are better protected. 7 to 14 days after full vaccination with one of the COVID-19 vaccines (AstraZeneca, Janssen, Pfizer or Moderna), 60-90% of vaccinated people are protected against COVID-19. This means that not everyone is protected. The chance of getting COVID-19 after full vaccination is very small, but not zero. There is currently no data on how long the vaccine will offer protection.
Five reasons why COVID herd immunity is probably impossible
Nature.com, March 18, 2021
The threshold for herd immunity is generally achievable only with high vaccination rates, and many scientists had thought that once people started being immunized en masse, herd immunity would permit society to return to normal. Most estimates had placed the threshold at 60–70% of the population gaining immunity, either through vaccinations or past exposure to the virus. The key to herd immunity is that, even if a person becomes infected, there are too few susceptible hosts around to maintain transmission — those who have been vaccinated or have already had the infection cannot contract and spread the virus. It is still unclear whether the COVID-19 vaccines developed by Moderna and Pfizer–BioNTech protect people from becoming infected, or from spreading the virus to others. Even as vaccine roll-out plans face distribution and allocation hurdles, new variants of SARS-CoV-2 are sprouting up that might be more transmissible and resistant to vaccines. Higher rates of immunity can create selective pressure, which would favor variants that are able to infect people who have been immunized. Vaccines will almost inevitably create new evolutionary pressures that produce variants.