COVID-19 Evidence Alerts
from McMaster PLUSTM

Current best evidence for clinical care (more info)

Primary Prevention Harder T, Koch J, Vygen-Bonnet S, et al. Efficacy and effectiveness of COVID-19 vaccines against SARS-CoV-2 infection: interim results of a living systematic review, 1 January to 14 May 2021. Euro Surveill. 2021 Jul;26(28). doi: 10.2807/1560-7917.ES.2021.26.28.2100563.
PICO Terms
adult (P) asymptomatic infection (O) Comirnaty; Pfizer vaccine; BNT162b2; BioNTech/Fosun Pharma; mRNA (I/C) Johnson & Johnson vaccine; Janssen Pharmaceutical Companies; Ad26.COV2.S; non-replicating viral vector (I/C) placebo (I/C) Spikevax; Moderna vaccine; mRNA-1273 SARS-CoV-2; ModernaTX; mRNA (I/C) symptomatic infection (O) vaccine effectiveness (O) vaccine efficacy (O) Vaxzevria; AstraZeneca vaccine; ChAd0x1 nCOV-19; Covishield; non-replicating viral vector; adenovirus; University of Oxford/AstraZeneca; AZD1222 (I/C)

Evidence on COVID-19 vaccine efficacy/effectiveness (VE) in preventing asymptomatic SARS-CoV-2 infections is needed to guide public health recommendations for vaccinated people. We report interim results of a living systematic review. We identified a total of 30 studies that investigated VE against symptomatic and/or asymptomatic infection. In fully vaccinated individuals, VE against symptomatic and asymptomatic infections was 80-90% in nearly all studies. Fully vaccinated persons are less likely to become infected and contribute to transmission.

Discipline / Specialty Area Score
Family Medicine (FM)/General Practice (GP)
General Internal Medicine-Primary Care(US)
Public Health
Pediatrics (General)
Internal Medicine
Infectious Disease
Comments from MORE raters

Family Medicine (FM)/General Practice (GP) rater

This is relevant to my work. Limitations of the review are clearly stated. I found this a good read and informative.

General Internal Medicine-Primary Care(US) rater

This is a very important article that will help tremendously medical practice.

Infectious Disease rater

This is a moving target, obviously. It would be great if we could assemble knowledge about vaccine efficacy (VE), but it is a huge challenge. We do not know the duration of protection (which seems to be months but not years) or what new variations will come along. The ongoing nature of this systematic review is helpful; although, not everything will be published in the most timely manner.

Infectious Disease rater

This paper is a meta-analysis of studies of coronavirus vaccine efficacy. Once again, efficacy for both symptomatic and asymptomatic infections was high. This paper has limited relevance in the United States as all papers reviewed preceded the delta variant outbreak that is causing the vast preponderance of disease.

Pediatrics (General) rater

This is a timely review reporting on the effectiveness/efficacy of COVID-19 vaccines, all showing evidence of protection from infection. I am concerned though that the included studies were mostly observational with high risk of bias. Only 2 RCTs were included, with one of them being of good quality. We need more RCTs of high quality to examine vaccine effectiveness, as well as safety.