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A 3-month-old baby in Texas died four days after receiving a Moderna mRNA RSV vaccine approved only for adults, according to a report filed with the federal Vaccine Adverse Event Reporting System (VAERS), researcher Jessica Rose, Ph.D., reported.
Moderna’s mRNA respiratory syncytial virus (RSV) vaccine, marketed as mRESVIA, is not authorized for infants or children. It is approved for adults age 60 and older and 18-59 for those at increased risk of severe RSV disease.
According to VAERS ID 2880791, an infant received the vaccine on Dec. 1, 2025. He subsequently developed lethargy, had difficulty staying awake and developed a low-grade fever.
The report states that the baby died around 2 a.m. on Dec. 5, 2025, and that his death was attributed to sudden infant death syndrome (SIDS).
Although the report listed the date of death as four days after vaccination, another database field indicated that the death occurred on the same day as vaccination, leaving uncertainty about the timeline of the infant’s death, according to Rose.
Rose also identified a second VAERS report involving a 17-year-old who received mRESVIA despite not meeting the approved age. According to that report, the vaccine was ordered outside Centers for Disease Control and Prevention (CDC) criteria. No adverse reactions or treatment were reported.
Overall, Rose identified 72 VAERS reports associated with mRESVIA. Of those, 20% were classified as serious, and 37.5% were filed on the same day as vaccination.
VAERS is a passive surveillance system jointly managed by the U.S. Food and Drug Administration (FDA) and CDC that can be used by healthcare providers and others to report adverse health events following vaccination. Reports alone don’t establish that a vaccine caused an issue, but they signal possible safety issues that warrant further investigation.
Although reports in VAERS require verification before they can be confirmed as vaccine-related injuries or deaths, the system has historically been shown to report only 1% of actual vaccine adverse events.
Rose also noted that mRESVIA has not yet been widely used. She said that given the number of reports already in VAERS, there are serious concerns with the safety of the drug.
Road to RSV vaccines for infants paved with failures
The FDA shut down a trial of two Moderna mRNA RSV vaccines for babies, including mRESVIA, in 2024 after the shots were linked to severe side effects in infants.
Exclusive reporting by The Defender today also revealed that since the trial was halted, 7% of vaccinated babies in the trial reportedly experienced serious unexplained adverse effects — and adverse events linked to the drug continued to be reported long after the trial was shut down.
The researchers suggested that Moderna may have misrepresented the safety data from its infant trials when the drugmaker presented the data to regulators.
Efforts to develop RSV vaccines for infants and children have been marked by safety concerns for decades.
In the 1960s, an experimental RSV vaccine made with inactivated virus was linked to the deaths of two toddlers. During the same trial, 80% of vaccinated children required hospitalization for severe RSV illness, a phenomenon known as vaccine-associated enhanced respiratory disease (VAERD). The trial ended in 1967, setting back RSV vaccine development for decades.
More recently, pharmaceutical companies renewed efforts to develop RSV vaccines for infants and children, but several trials encountered setbacks.
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In June 2023, GSK discontinued a clinical trial of its RSV vaccine for pregnant women after researchers identified a 37% higher risk of preterm birth among vaccinated participants.
Pfizer’s comparable maternal RSV vaccine received regulatory approval, although a higher incidence of preterm births among vaccinated women was observed in both clinical trial data and post-marketing research.
In October 2024, Sanofi suspended a pediatric RSV vaccine trial, citing insufficient efficacy. However, trial documents revealed that an infant had died during the study. Sanofi maintained that the death was unrelated to its vaccine.
Although RSV vaccines have not been approved for infants, monoclonal antibody injections have been authorized to protect babies against the virus. Unlike vaccines, these products deliver antibodies directly rather than stimulating the body to produce its own.
In December 2025, the FDA said it would examine the safety of two such products — Sanofi and AstraZeneca’s Beyfortus and Merck’s Enflonsia — following reports of infant deaths during clinical trials, but has not reported on those investigations.
Related articles in The Defender
- Exclusive: Moderna RSV Vaccine Trial in Babies Linked to Severe RSV, Other Serious Injuries
- ‘Not Ready for Prime Time’? FDA Approves First mRNA Flu Vaccine Despite Safety Concerns
- Moderna Shuts Down mRNA RSV Vaccine Trial in Babies After Shots Linked to Severe Side Effects, FDA Document Reveals
- Exclusive: Moderna RSV Vaccine Trial in Babies Linked to Severe RSV, Other Serious Injuries
- Half of SIDS Cases Occurred Within 48 Hours of Vaccination, Former Police Detective Says
