Immune responses associated with coadministered seasonal inactivated influenza and respiratory syncytial virus (RSV) perfusion F-protein-based vaccines are noninferior to those associated with receipt of either vaccine alone, according to study results published in Clinical Infectious Diseases.
Researchers conducted a phase 3, randomized, double-blinded, placebo-controlled trial among older adults (age, ≥65 years) at 31 sites in Australia from April 13 to October 12, 2022. Eligible patients included healthy men and women, as well as those with preexisting stable disease. Exclusion criteria were severe chronic disorders, a history of Guillain-Barre syndrome, a history of vaccine allergies, RSV or influenza vaccination within the past 6 months, and immunocompromised status.
Patients were randomly assigned 1:1 to receive either coadministered seasonal inactivated influenza plus RSV perfusion F-protein (Visit 1) vaccines followed by placebo (Visit 2) or sequentially administered influenza and RSV vaccines alone plus placebo (Influenza at Visit 1; RSV at Visit 2) vaccine plus placebo.
The primary immunogenicity objectives were to demonstrate noninferior immune responses between patients in the coadministration and sequential administration groups. Immune responses elicited by the RSV and influenza vaccines were measured via RSV-A and RSV-B neutralizing titers and strain-specific hemagglutination inhibition (HAI) titers, respectively. Blood samples were collected at Visit 1 prior to vaccination and 1 month after vaccination at Visit 2.
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Although this study was conducted in older adults, we expect that the favorable safety profile and robust immunogenicity observed with coadministration would support broader application.
A total of 1403 patients were included in the analysis, of whom 703 were in the coadministration group and 698 were in the sequential administration group. In both groups, most patients adhered to the study protocol (97.3% and 99.1%, respectively), and baseline characteristics were well balanced (median age, 70 [range, 65-91] years; 55% women; 95% White).
Overall, 45% of patients reported current or former smoking status, and most (~95%) reported preexisting conditions, particularly respiratory (~22%) and cardiac (~17%) conditions.
At 1-month, geometric mean ratios for coadministration to sequential administration were 0.86 and 0.85 for RSV-A and for RSV-B titers, respectively, and ranged from 0.77 to 0.90 for strain-specific HAI titers. Further analysis among all subgroups showed a 1.5-fold prespecified noninferiority margin, indicating the primary immunogenicity objectives were achieved.
Between baseline and 1 month after vaccination, geometric mean fold rises of RSV 50% neutralizing titers indicated robust immune responses among patients in both groups. Moreover, similar rates of seroprotection and seroconversion were observed for 4 influenza strains.
In regard to safety, most local reactions and systemic events among patients in the coadministration group were of mild to moderate severity. The most common local reaction was injection site pain, and the most common systemic events were fatigue and headache. The overall rate of severe adverse events was low (range, 1.1%-0.9%), and none were attributed to vaccination.
Limitations of this study include the older patient population and the lack of data from individuals with immunocompromised conditions.
“Although this study was conducted in older adults, we expect that the favorable safety profile and robust immunogenicity observed with coadministration would support broader application,” the researchers concluded.
Disclosure: This research was supported by Pfizer Inc., and multiple study authors reported affiliations with industry. Please see the original reference for a full list of disclosures.
This article originally appeared on Infectious Disease Advisor
