Concurrent administration of the Pfizer/BioNTech bivalent COVID-19 vaccine and the seasonal flu vaccine was as effective against poor outcomes as giving the shots separately, which could increase uptake of both, suggests a study by scientists from Pfizer and Genesis Research.
The study, published yesterday in JAMA Network Open, used claims data to compare the effectiveness of the vaccines against hospitalization, emergency department (ED) visits, urgent care (UC), and outpatient visits when given separately or together among 3,442,996 US adults from August 2022 to January 2023.
Average age was 65 years, 57% were women, and all had either private health insurance or Medicare Advantage coverage. In total, 627,735 participants (18.2%) received the COVID-19 and flu vaccines at the same time, while 369,423 (10.7%) received the COVID-19 vaccine alone, and 2,445,838 (71.0%) had the flu vaccine alone. Median days of follow-up were 109 for the coadministration group, 51 for the COVID-only group, and 90 for flu-only participants.
Based on data from clinical trials suggesting that the two vaccines can be safely given at the same time, the Centers for Disease Control and Prevention (CDC) revised its recommendations to allow coadministration, the study authors noted.
"While some high-risk individuals may receive boosters more frequently, it is anticipated that COVID-19 vaccines will likely be administered annually alongside seasonal influenza vaccines (SIVs) each autumn or winter for the foreseeable future," they wrote.
Similar rates of COVID hospitalization and ED, UC, outpatient visits
Among the 2,210,493 participants aged 65 years or older, the coadministration group had a similar rate of COVID-19 hospitalization (adjusted hazard ratio [AHR], 1.04) and a slightly higher rate of ED or UC visits (AHR, 1.12) and outpatient visits (AHR, 1.06) than the COVID–only group.
Among the 1,232,503 adults aged 18 to 64 years, the rate of COVID-related outcomes was slightly higher among those who received both vaccines at the same time versus the COVID-19 vaccine alone (AHR point estimate range, 1.14 to 1.57), but fewer events overall in this age-group resulted in wider confidence intervals (CIs).
In general, compared with those who received the flu vaccine alone, the coadministration group had a slightly lower rate of most flu-related outcomes (AHR point estimates, 0.83 to 0.93 for those aged 65 years or older vs 0.76 to 1.08 for those 18 to 64 years).
May boost coverage of both vaccines
Negative control outcomes pointed to residual bias, and calibration of COVID- and flu-related outcomes with negative controls pushed estimates closer to the null, with most CIs crossing 1.00, suggesting no meaningful differences in effectiveness for the coadministration group. After calibration with negative control outcomes, coadministration of the vaccines appeared similarly effective as those given separately.
These data support coadministration of SIV with COVID-19 boosters during future autumn or winter vaccination campaigns, which may improve uptake for both of these underutilized and potentially life-saving public health interventions.
"To our knowledge, no data describing the impact of coadministration of COVID-19 vaccines and SIV were available before our study," the researchers wrote.
"These data support coadministration of SIV with COVID-19 boosters during future autumn or winter vaccination campaigns, which may improve uptake for both of these underutilized and potentially life-saving public health interventions," they added.