TOPLINE:

In healthy, nonpregnant women, the multidose vial presentation of the respiratory syncytial virus prefusion F protein vaccine (RSVpreF) matched the licensed single-dose vial in neutralizing immune responses to both RSV A and RSV B and showed a comparable safety profile.

METHODOLOGY:

• Researchers conducted a phase 3 randomized trial at six sites in the US to assess the immunogenicity, safety, and tolerability of the RSVpreF vaccine given as a multidose vial vs a single-dose vial.
• A total of 450 healthy, nonpregnant, and nonbreastfeeding women aged 18-49 years were randomly assigned and vaccinated: 223 received the multidose vial presentation containing the preservative 2-phenoxyethanol, and 227 received the preservative-free single-dose vial presentation.
• Both presentations were administered as a single 0.5-mL intramuscular injection containing 120 µg of RSVpreF antigen per dose; the multidose presentation was supplied as a vial containing three doses.
• The primary endpoints included geometric mean titers against RSV A and RSV B before and 1 month after vaccination; noninferiority required the lower bound of the 95% CI for the geometric mean ratio (multidose to single dose) to exceed 0.67 for both RSV A and RSV B.
• Secondary endpoint was the proportion of women achieving a seroresponse, which was a significant rise from baseline in levels of neutralizing antibody at 1 month; safety endpoints were also assessed.

TAKEAWAY:

• The geometric mean ratios comparing multidose to single-dose group were 0.96 (95% CI, 0.84-1.10) for RSV A and 0.91 (95% CI, 0.79-1.06) for RSV B, meeting the noninferiority criteria for both.
• The rates of seroresponse at 1 month were high and comparable, with the rates being 92% in both groups for RSV A and 97% in the multidose group vs 91% in the single-dose group for RSV B.
• The percentages of women reporting local reactions and those reporting systemic events within 7 days after vaccination were similar between groups; most systemic events were mild to moderate in severity.
• Adverse events through 1 month after vaccination were similar between groups, with most being mild to moderate. No adverse events of special interest, withdrawals due to adverse events, or deaths were reported.

IN PRACTICE:

“The lower cost and cold-chain capacity requirements of the MDV [multidose vial] vs SDV [single-dose vial] presentation may be particularly important for facilitating immunization efforts in LMICs [lower- to middle-income countries], which, in turn, could lead to substantial reductions in the global burden of RSV-associated illness,” the authors wrote.

SOURCE:

The study was led by Uzma N. Sarwar, Vaccine Research and Development, Pfizer, Inc., New York City. It was published online on January 29, 2026, in eClinicalMedicine.

LIMITATIONS:

The trial was open-label, which may have biased how subjective outcomes were reported. It tested only the first dose drawn from the multidose vial rather than all three doses intended for real-world use. The study population did not match the intended vaccine recipients, and the short follow-up duration made it hard to assess long-term immune responses and safety. 

DISCLOSURES:

The study was funded by Pfizer. Twelve authors reported being employees of Pfizer and potentially holding stock or stock options. Two authors reported receiving compensation from Pfizer, and one author reported receiving compensation from multiple pharmaceutical companies.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.