Bivalent COVID-19 Boosters, Nirmatrelvir-Ritonavir Most Beneficial in Older Patients

High uptake of bivalent COVID-19 boosters and nirmatrelvir-ritonavir uptake was predicted to avert a significant number of COVID-19 diagnoses and severe outcomes, especially among older patients.

High uptake of bivalent boosters and nirmatrelvir-ritonavir for the prevention of severe COVID-19 outcomes is most beneficial in older patients, though their use does not address the overall burden of disease, according to study results published in Open Forum Infectious Diseases. 

Researchers conducted a modeling study with deidentified person-level COVID-19 data from the California Department of Public Health from July 2022 to January 2023. The researchers aimed to determine whether increasing the uptake of bivalent COVID-19 boosters and nirmatrelvir-ritonavir reduces diagnoses and severe COVID-19 outcomes in high-risk populations. Collected data included positive SARS-CoV-2 molecular test results, reports of COVID-19-related hospitalization and mortality, and COVID-19 vaccination status (full, partial, or boosted).  

Study patients were stratified by age group, including those aged 0 to 17, 18 to 49, 50 to 64, 65 to 74, 75 to 84, and those aged 85 years and older. Of note, patients who were partially vaccinated were classified as fully vaccinated as they represented less than 4% of total COVID-19 outcomes.

The primary outcomes included COVID-19 diagnosis, COVID-19-related hospitalization, and COVID-19-related mortality. The researchers used quasi-Poisson regression models to predict the number of weekly COVID-19 outcomes by age group and vaccine status over a 6-month period. Data captured from these models were then used to estimate total the number of averted outcomes, including number needed to treat (NNT), associated with each intervention (ie, bivalent booster or nirmatrelvir-ritonavir receipt).

This study provides evidence on the public health benefit of utilizing both interventions in the United States and highlights potential opportunities for policymakers to improve the promotion and accessibility of these live-saving interventions.

A total of 1,128,004 confirmed COVID-19 diagnoses were included in the final analysis, of which 43,684 (3.9%) and 5876 (0.5%) were COVID-19-related hospitalizations and mortality events, respectively. Patients aged 65 and older accounted for more than 60% of hospitalizations and 83% of mortality events. At baseline, 82% of patients were partially vaccinated, 73% were fully vaccinated, and 60% had received a booster. The rate of bivalent booster administration was highest among patients 65 years and older, representing 36% of all booster doses received.

Within a period of 6 months, the regression model predicted the occurrence of 1,174,195 (95% CI, 985,150-1,403,574) COVID-19 diagnoses, 48,893 (95% CI, 42,503-56,281) hospitalizations, and 7189 (95% CI, 6239-8311) mortality events.

Further analysis showed that bivalent booster coverage among 70% of the overall population was predicted to avert 187,201 (95% uncertainty interval [UI], 168,691-205,233; NNT, 111) COVID-19 diagnoses, 9066 (95% UI, 6736-10,511; NNT, 2273) hospitalizations, and 1811 (95% UI, 1394-2375; NNT, 11,378) mortality events.

Receipt of an additional bivalent booster dose in patients aged 65 years and older was predicted to avert 10,794 (95% UI, 9439-12,333; NNT, 177) COVID-19 diagnoses, 2725 (95% UI, 1923-3275; NNT, 698) hospitalizations, and 690 (95% UI, 527-855; NNT, 2757) mortality events. For unvaccinated patients, receipt of a bivalent booster dose was predicted to avert 95,458 (95% UI, 87,586-101,917; NNT, 50) COVID-19 diagnoses.

Nirmatrelvir-ritonavir uptake of 70% in eligible populations was predicted to avert 4809 (95% UI, 3365-5813; NNT, 18) hospitalizations and 1292 (95% UI, 798-1594; NNT, 67) mortality events. The predicted number of averted hospitalizations (4458; 95% UI, 3121-5388; NNT, 14) and mortality events (1252; 95% UI, 778-1537; NNT, 50) was similar in patients aged 65 years and older. 

Limitations of this study include the reliance on historical data, the possibility of underpredicted COVID-19 outcomes, and the lack of data on the effect of prior COVID-19 infection and immunocompromised status.

In regard to bivalent boosters and nirmatrelvir-ritonavir, “This study provides evidence on the public health benefit of utilizing both interventions in the United States and highlights potential opportunities for policymakers to improve the promotion and accessibility of these live-saving interventions,” the researchers concluded.

This article originally appeared on Infectious Disease Advisor


Park HJ, Tan ST, Leon TM, Jain S, Schechter R, Lo NC. Predicting the public health impact of bivalent vaccines and nirmatrelvir-ritonavir against COVID-19. Open Forum Infect Dis. Published online August 9, 2023. doi:10.1093/ofid/ofad415.