Abstract
Although multiple studies revealed high vaccine effectiveness of coronavirus disease 2019 (COVID-19) vaccines within 3 months after the completion of vaccines, long-term vaccine effectiveness has not been well established, especially after the δ (delta) variant became prominent. We performed a systematic literature review and meta-analysis of long-term vaccine effectiveness. We searched PubMed, CINAHL, EMBASE, Cochrane Central Register of Controlled Trials, Scopus, and Web of Science from December 2019 to November 15, 2021, for studies evaluating the long-term vaccine effectiveness against laboratory-confirmed COVID-19 or COVID-19 hospitalization among individuals who received 2 doses of Pfizer/BioNTech, Moderna, or AstraZeneca vaccines, or 1 dose of the Janssen vaccine. Long-term was defined as >5 months after the last dose. We calculated the pooled diagnostic odds ratio (DOR) with 95% confidence interval for COVID-19 between vaccinated and unvaccinated individuals. Vaccine effectiveness was estimated as 100% × (1 - DOR). In total, 16 studies including 17,939,172 individuals evaluated long-term vaccine effectiveness and were included in the meta-analysis. The pooled DOR for COVID-19 was 0.158 (95% CI: 0.157-0.160) with an estimated vaccine effectiveness of 84.2% (95% CI, 84.0- 84.3%). Estimated vaccine effectiveness against COVID-19 hospitalization was 88.7% (95% CI, 55.8%-97.1%). Vaccine effectiveness against COVID-19 during the δ variant period was 61.2% (95% CI, 59.0%-63.3%). COVID-19 vaccines are effective in preventing COVID-19 and COVID-19 hospitalization across a long-term period for the circulating variants during the study period. More observational studies are needed to evaluate the vaccine effectiveness of third dose of a COVID-19 vaccine, the vaccine effectiveness of mixing COVID-19 vaccines, COVID-19 breakthrough infection, and vaccine effectiveness against newly emerging variants.
Highlights
Multiple studies revealed high vaccine effectiveness of coronavirus disease 2019 (COVID-19) vaccines within 3 months after the completion of vaccines, long-term vaccine effectiveness has not been well established, especially after the δ variant became prominent
The first coronavirus disease 2019 (COVID-19) vaccine was authorized for emergency use by the US Food and Drug Administration on December 11, 2020.1 Over the past several months, research studies have yielded substantial data on shortterm (≤ 3 months) vaccine effectiveness[2,3,4] against symptomatic COVID-19
Antimicrobial Stewardship & Healthcare Epidemiology, https://doi.org/10.1017/ ash.2021.261 known to be very high at 95% for the Pfizer/BioNTech COVID
Summary
We searched PubMed, CINAHL, EMBASE, Cochrane Central Register of Controlled Trials, Scopus, and Web of Science from December 2019 to November 15, 2021, for studies evaluating the long-term vaccine effectiveness against laboratory-confirmed COVID-19 or COVID-19 hospitalization among individuals who received 2 doses of Pfizer/BioNTech, Moderna, or AstraZeneca vaccines, or 1 dose of the Janssen vaccine. Systematic literature review and inclusion and exclusion criteria. The inclusion criteria for studies in this systematic review were as follows: original research manuscripts; published in peerreviewed scientific journals; involved vaccinated and unvaccinated individuals; evaluated the long-term effectiveness of COVID-19 vaccine; and observational study design. Long-term was defined as >5 months after the second dose for mRNA (Pfizer/ BioNTech or Moderna) or AstraZeneca COVID-19 vaccine, or 1 dose of Janssen COVID-19 vaccine. Studies without comparison between vaccinated and unvaccinated individuals (or other vaccinated control group), and studies without vaccine effectiveness data were excluded
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