The World Health Organization has prequalified a multi-dose vial version of the maternal RSV vaccine, clearing the last regulatory obstacle that had been holding up a funded global rollout aimed at protecting newborns in the countries where RSV kills the most infants.
The decision, announced on September 9, covers the multi-dose presentation of RSVpreF, sold by Pfizer as Abrysvo. Gavi, the vaccine alliance, welcomed the decision and said it paves the way for introduction in lower-income countries with its support.
The organization does not regulate the American market, and the decision changes nothing about what a pregnant patient in Houston or Atlanta can receive. It arrives, however, at the point in the calendar when US maternal RSV vaccination is meant to begin, which makes the underlying question identical on both sides of the world: how do you get protection to a baby before the virus finds them.
A Packaging Decision with Real Consequences for Cold Chains
Prequalification of the single-dose version happened in March 2025. That sounds like the hard part was already done, but it was not.
As Gavi explained why multi dose vials matter, multi-dose formulations require a separate assessment, because changes to formulation and packaging can call for additional immunogenicity and stability testing. Multi-dose vials also reduce the cost, packaging volume, refrigerated storage space and medical waste attached to each dose. Fewer vials for the same number of patients means less room taken on a delivery truck and less strain on the chain of refrigeration that carries a vaccine from factory to clinic.
In health systems where reliable cold storage is the binding constraint rather than the vaccine itself, that arithmetic decides whether a program is feasible. The presentation was developed with support from the Gates Foundation.
Ignacio Esteban, a senior policy manager at Gavi, called the decision "a key milestone for RSV and, more broadly, for pneumonia prevention" and for reducing infant mortality globally.
Gavi Countries Can Now Move From Approval Toward Rollout
Gavi's board approved a maternal RSV vaccine program for its 2026 to 2030 strategic period, and the alliance agreed in July 2025 to make funding available. Introduction was conditional on a prequalified multi-dose vial being available. That condition is now met, and eligible countries can apply for funding support to fold maternal immunization into routine care.
The burden numbers explain the urgency. RSV causes an estimated 33 million lower respiratory tract infections, 3.6 million hospitalizations and more than 100,000 deaths among children under five each year. Almost half of those deaths occur in infants younger than six months, the exact group maternal vaccination is designed to cover.
Around 97% of RSV deaths occur in low- and middle-income countries, with the heaviest burden in Africa. In many of those settings, children die at home before reaching a facility that could provide oxygen or respiratory support.
Maternal immunization works by prompting the pregnant patient to make antibodies that cross the placenta before birth, protecting the infant through roughly the first six months. WHO recommends giving it in the third trimester, from week 28 onward, and advises countries to introduce either the maternal vaccine or a long-acting monoclonal antibody for infants.
American Parents Face a Different Set of Choices This Month
For households in the United States, the relevant decision is not about vials. It is about which of two products to use, and when.
CDC guidance for pregnant patients recommends a single dose of Abrysvo at 32 through 36 weeks of gestation, administered September through January in most of the continental United States. Patients further along than 36 weeks and six days are not advised to get it, because there is not enough time for antibodies to develop and cross the placenta. That CDC page was last updated in 2024, and obstetric groups have since gone further: an updated obstetric practice advisory states that patients in most of the continental United States are eligible from September 1 through March 1. Anyone outside the narrower window should ask their own clinician which schedule that practice follows.
The alternative is protecting the baby directly. Under CDC's infant antibody guidance, infants whose mothers were not vaccinated during the current pregnancy, whose vaccination status is unknown, or who were born within 14 days of maternal vaccination are recommended to receive a monoclonal antibody. Two are available for infants younger than eight months in their first season, nirsevimab and clesrovimab, with no stated preference between them. For children aged 8 through 19 months at increased risk who are entering a second season, only nirsevimab is recommended. Infant antibodies are given October through March in most of the country.
Most infants need one approach, not both. Which one fits depends on due date, gestational age now, and family preference, and that is a conversation for an obstetric or pediatric visit in the next few weeks rather than in December.
Seasonality varies. Alaska and tropical areas including southern Florida, Guam, Hawaii, Puerto Rico, the US Virgin Islands and the US-affiliated Pacific Islands follow different local timing, and families there should check state or territorial guidance. Current national activity is tracked on CDC's respiratory illness data pages.
Cost should not be the barrier it once was. The maternal vaccine and infant antibodies are covered under the Vaccines for Children program for eligible children and are generally covered as preventive services by commercial plans and Medicaid, though families should confirm coverage and ask about in-network administration. Local health departments in most major metro areas administer both.
Remaining Gaps in Supply, Timing and Equity
Several things are still unsettled, and the honest framing matters here.
Prequalification is a quality and suitability determination, not a delivery schedule. No country introduction dates have been announced, and Gavi has not published which countries will go first or how quickly procurement will move. Whether supply can meet demand at the new price point is unknown.
Multi-dose vials also carry their own operational challenges. Each dose must be drawn with a sterile needle, the opened vial has to be stored properly and discarded within a set time, and doses can be wasted when few patients turn up at a session. Programs have to manage that.
The rollout will not affect American vaccine supply, and it does not signal any change to US recommendations. What it may eventually influence is the global evidence base on maternal immunization at scale, which is the kind of data that shapes later guidance everywhere.
For now, the useful action for a US household is unrelated to Geneva. If someone in the family is between 32 and 36 weeks pregnant, or has a baby who will be younger than eight months during this season, this is the month to settle which RSV protection that baby will get.
Key Questions Answered
What did WHO decide? It prequalified a multi-dose vial presentation of the maternal RSV vaccine RSVpreF, marketed as Abrysvo, in a decision announced on September 9.
Why does the vial format matter? Multi-dose vials lower per-dose cost and reduce packaging, cold storage requirements and medical waste, which makes large-scale programs practical in lower-income health systems.
Does this change vaccine availability in the United States? No. The maternal RSV vaccine has been available in the US since 2023, and WHO prequalification does not affect US supply or recommendations.
How severe is RSV in infants globally? Estimates cited by WHO and Gavi put the annual toll at 33 million lower respiratory tract infections, 3.6 million hospitalizations and more than 100,000 deaths in children under five, with almost half of deaths in infants under six months.
When should a pregnant patient in the US get the vaccine? CDC recommends a single dose at 32 through 36 weeks of gestation, given September through January in most of the continental United States. Obstetric guidance extends eligibility to March 1.
What if someone is past 36 weeks and six days? CDC advises against maternal vaccination at that point and recommends the infant receive a monoclonal antibody instead. That decision should be made with a clinician.
Do babies need both the maternal vaccine and the antibody? Most do not. One approach is generally recommended, with limited exceptions such as birth within 14 days of maternal vaccination.
