Frågedatum: 2021-11-26
RELIS database 2021; id.nr. 540, ULIC
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Immunitet för Covid-19 vid den tredje sprutan



Fråga: Tappar man immunitet för Covid-19 när man får den tredje sprutan mer än tre månader efter den andra? Är det som att börja om från början?

Svar: The answer is no for both questions.

Follow-up data of vaccine effectiveness in the USA has shown that effectiveness remains for at least 6 months after full vaccination, but that a decline can be observed.

Among adults <65 years of age, vaccines remain effective in preventing hospitalization and severe disease. However, recent data (1, 2) suggest vaccination effectiveness in terms of preventing infection or milder illness decreases over time (1, 2). There was a significant decline in vaccine effectiveness (the incidence rates of e.g., positive SARS-CoV-2 testing) in individuals =65 years of age for mRNA products in the Delta period in the USA. There was a smaller decline in vaccine effectiveness in terms of hospitalization in individuals =65 years of age (2).

From January to July 2021 in Minnesota (3), the effectiveness estimates of Moderna (mRNA-1273) and Pfizer/BioNTech (BNT162b2) in preventing SARS-CoV-2 infection with onset at least 14 days after the second dose were 86% (95% CI: 81–90.6%, p=1.6×10-42) and 76% (95% CI: 69–81%, p=1.3×10-31), respectively. With increasing cases in Minnesota during July, the effectiveness against infection was lower for mRNA-1273 (76%, 95% CI: 58–87%) compared to prior months, with an even more pronounced reduction for BNT162b2 (42%, 95% CI: 13–62%). This lower effectiveness, according to CDC, is likely due to the combination of decreasing protection as time passes since getting vaccinated, as well as the greater infectiousness of the Delta variant (1, 2).

Therefore, the CDC recommends that people who have received a primary mRNA COVID-19 vaccine series and are 65 years and older, 50–64 years with underlying medical conditions, or 18 years and older who live in long-term care settings should receive a booster shot at least 6 months after completing the primary series (which may include an additional primary dose in persons with moderate to severe immunocompromise) (1).

Referenser:
  1. COVID-19 Vaccine Booster Shots. Updated Nov. 9, 2021. https://www.cdc.gov/coronavirus/2019-ncov/vaccines/booster-shot.html
  2. https://www.cdc.gov/vaccines/acip/meetings/downloads/slides-2021-9-23/03-COVID-Oliver.pdf
  3. Puranik A, Lenehan PJ, Silvert E, et al. Comparison of two highly-effective mRNA vaccines for COVID-19 during periods of Alpha and Delta variant prevalence. Preprint. medRxiv. 2021;2021.08.06.21261707. Published 2021 Aug 9. doi:10.1101/2021.08.06.21261707