Duration of effectiveness of vaccines against SARS-CoV-2 infection and COVID-19 disease: results of a systematic review and meta-regression.
Level 1 - systematic review of randomized trials
Systematic review and meta-regression of clinical trials and observational studies
PubMed 35202601 · doi:10.1016/S0140-6736(22)00152-0
What was done
Authors conducted a systematic review and random-effects meta-regression across preprint and peer-reviewed databases from June 17 to December 2, 2021. They included randomized trials and observational studies evaluating Pfizer-BioNTech, Moderna, Janssen, or AstraZeneca vaccines that reported efficacy or effectiveness at discrete time intervals up to 6 months post-vaccination. Risk of bias was evaluated with RoB 2 for trials and ROBINS-I for non-randomized studies.
What was found
Eighteen studies (78 vaccine-specific evaluations) were included. Between 1 and 6 months after full vaccination, vaccine effectiveness against infection decreased by 21.0 percentage points (95% CI 13.9-29.8) in all ages and 20.7 percentage points (95% CI 10.2-36.6) in older adults (≥50 years). For symptomatic COVID-19, effectiveness fell by 24.9 percentage points (95% CI 13.4-41.6) in all ages and 32.0 percentage points (95% CI 11.0-69.0) in older adults. Protection against severe disease decreased by 10.0 percentage points (95% CI 6.1-15.4) in all ages and 9.5 percentage points (95% CI 5.7-14.6) in older adults, with 81% of severe disease estimates remaining above 70%.
Why it matters
These findings quantify the rate of immune waning across major COVID-19 vaccines prior to Omicron, demonstrating substantial drops in protection against transmission and symptomatic illness but robust retention of protection against severe disease over 6 months.
Limits
All included studies were conducted before widespread circulation of the Omicron variant. Study quality was heterogeneous: only 3 studies had low risk of bias, while 8 had moderate and 7 had serious risk of bias. Duration was limited to 6 months.
Cited by
- supports With the Delta variant, COVID-19 vaccine effectiveness against transmission decreased compared to earlier in the pandemic, but protection against hospitalization and severe disease remained largely preserved.