Estimation of COVID-19 mRNA vaccine efficacy and COVID-19 disease and severity by vaccination status during the Omicron BA.4 and BA.5 sublineage periods.
Key points
What is the estimated vaccine effectiveness (VE) associated with the first-generation COVID-19 mRNA vaccines against medically managed COVID-19 during the predominance of the Omicron BA.4 and BA.5 sublineages?
Findings
This case-control study included 82,229 ED or urgent care encounters and 21,007 hospitalizations for COVID-19-like illnesses. Among hospitalized patients, vaccine effectiveness (VE) with 3 doses was 68% for those with the third dose 7 to 119 days before, but was lower 120 days or more after vaccination (VE, 36%). .
Meaning
These findings suggest that first-generation COVID-19 mRNA vaccines were associated with protection against COVID-19 during the predominant periods of the Omicron BA.4/BA.5 sublineage, but protection diminished over time.
Comments
A multistate study from the US Centers for Disease Control and Prevention (CDC) VISION Network found that first-generation COVID-19 mRNA vaccines were associated with protection against COVID-19 during the periods of predominance of Omicron BA.4/BA.5.
The new analysis found that mRNA vaccines protected against COVID-19-associated hospitalization and ICU admission or death in hospital and observed less severe disease during BA.4/BA.5 dominance compared with the previous Omicron variants.
During the dominance of BA.4/BA.5, the estimated efficacy of the 3-dose vaccine against hospitalization was 68% between days 7 and 119 post-vaccination. The vaccine’s effectiveness against hospitalization decreased to 36 percent at 120 days or more after vaccination.
For hospitalization, an indicator of severe disease, the estimated vaccine efficacy of three doses for all adults and four doses for adults aged 50 years and older was similar to that reported during the prevalence of previous Omicron variants. However, hospitalized adults were less likely to be admitted to the ICU or die in hospital and had a shorter length of stay during the BA.4/BA.5 predominance compared to previous Omicron variants.
“Our findings that COVID-19 mRNA vaccines remain effective and that vaccinated adults were not as sick during the dominance of BA.4/BA.5 are encouraging as we look toward the development of future vaccines and strategies.” to combat the virus,” said co-author Shaun Grannis, MD, MS, vice president of data and analytics at the Regenstrief Institute.
"Estimation of COVID-19 mRNA Vaccine Efficacy and COVID-19 Disease and Severity by Vaccination Status During the Omicron BA.4 and BA.5 Sublineage Periods," is published in JAMA Network Open .
The study authors note that estimating the effectiveness of the COVID-19 vaccine “has become complex as additional booster doses of the vaccine are authorized, vaccine-induced protection wanes over time, new variants have emerged or subvariants and the majority of the US population has experienced a previous infection (57-94%, depending on the source).”
“As new variants emerge, continued monitoring of vaccine effectiveness is critical to inform public health strategies and patient treatment,” said study co-author Brian Dixon, PhD., MPA, acting director of the Center for Biomedical Informatics of the Regenstrief Institute. “Monitoring vaccine performance will also help develop better vaccines and inform best practices for future pandemics.”
This new study analyzed 82,229 emergency or urgent care department encounters and 21,007 hospitalizations for COVID-19-like illnesses in adults 18 years and older. Nine VISION sites in 10 states contributed data, including 268 hospitals, 292 emergency departments, and 140 urgent care clinics.
The authors state: “The estimated vaccine was similar across outcomes, contradicting many previous studies of vaccine effectiveness, including previous VISION studies, which have tended to show greater vaccine-associated protection for more severe outcomes.” . This could be due to changes in the immunity of the reference population (e.g., most adults now have evidence of previous infection), changes in behavior (e.g., less use of social distancing and masks during the last few months) or residual confounding factors.”
Conclusions and relevance In this case-control study of COVID-19 vaccines and disease, vaccine effectiveness (VE) associated with protection against medically managed COVID-19 disease was lower with increasing time since last dose ; Vaccine effectiveness (VE) was higher after receiving 1 or 2 booster doses compared to a primary series alone. |
