Withheld: Real-World Infant Deaths from RSV Antibody Shot

Withheld: Real-World Infant Deaths from RSV Antibody Shot
by Yaffa Shir-Raz at Brownstone Institute

As ACIP deliberated without access to full trial data, an even more alarming pattern was already unfolding in the real world. Now, analysis of the FDA’s FAERS database reveals 37 infant deaths out of just 991 reports – a fatality signal nearly twice that of other routine vaccines. Why was this not disclosed?

The warning sign was already visible in the clinical trials: infant deaths in the treatment groups were twice as frequent as in the control arms – a signal that should have triggered immediate scrutiny. As documented in a previous Brownstone article, this alarming imbalance was withheld from ACIP during its June 2025 review of Merck’s competing RSV antibody, Clesrovimab.

Now it emerges that this was not the only red flag kept from the committee. An analysis of real-world data from the FDA’s adverse event reporting system (FAERS) reveals an even starker reality: since Sanofi’s Beyfortus (nirsevimab), which was approved and added to the US infant immunization schedule in 2023, there have been 1,012 adverse event reports – including 37 infant deaths, a concentration rarely seen in pediatric vaccine safety profiles.

A Disproportionate Share of Deaths

As of September 29, 2025, the FAERS database lists 1,012 adverse event reports for Beyfortus, including 684 serious cases and 37 infant deaths (see Figure 1). This reflects a proportion of reported deaths of 3.6% – far higher than historical norms. A comprehensive CDC surveillance study (1991-2001) found that deaths typically comprised only 1.4% to 2.3% of all pediatric VAERS reports. A 2023 systematic review covering over three decades of VAERS data similarly found that deaths accounted for just 1.0% of all reports across all age groups, with most years staying below 2%, and only isolated spikes in the early 1990s exceeding that level. Against this backdrop, the proportion of reported Beyfortus cases involving infant deaths appears nearly double the historical average.

The overall severity profile is equally concerning. Of the 1,012 total Beyfortus reports in FAERS, 684 (67.4%) were classified as serious adverse events – defined as hospitalization, life-threatening conditions, disability, or death. As detailed above, this includes 37 infant deaths (3.6%). The remaining serious cases include 415 hospitalizations (40.9%) and 46 life-threatening events (4.5%). For comparison, the same CDC study found that only 14.2% of reports were classified as serious, while the 2023 systematic review reported hospitalization rates of just 5.8% and life-threatening events at 1.4% of all reports. These benchmarks underscore how disproportionately severe the adverse event profile is for Beyfortus.

While VAERS reports do not establish causality, they are widely used by regulators for signal detection. Importantly, even established passive surveillance systems such as VAERS are estimated to capture only 1-10% of actual adverse events. These patterns, even if preliminary, merit urgent investigation, not dismissal.

A Seasonal Mortality Pattern Hidden from Reviewers

At first glance, one might suggest that the rising number of deaths simply reflects the expansion of Beyfortus use. Yet the timeline tells a more nuanced story – one that reveals a growing and disproportionate signal, even before full-scale uptake.

Before examining the seasonal trends in detail, it is important to understand the scale of uptake. During the 2023–2024 RSV season – the first season in which either nirsevimab or the maternal RSV vaccine was available – CDC data show that only 29% of eligible infants were immunized through either route. State-level coverage ranged from just 11% to 53% (CDC, 2024). This limited adoption is critical context: if serious adverse events are already emerging at submaximal coverage, what will happen as usage expands?

The year-by-year timeline of deaths provides an instructive contrast:

• 2023: Beyfortus was rolled out only in October, with a limited three-month window before the season ended – and amid a nationwide shortage that restricted access mainly to high-risk infants. Just 2 deaths were reported that year.
• 2024: With supply restored, the drug was administered over a full RSV season – six months in total (January–March, then again October–December). Reports surged to 15 deaths.
• 2025: By September, after only the first three months of that year’s coverage period, 20 infant deaths had already been reported – surpassing the prior year’s total, even before the 2025–2026 season began.

This pattern undercuts the notion that the signal is merely an artifact of broader use. If more months and more doses were the only explanation, the number of reported deaths should scale more gradually. Instead, the data show a sharp escalation – even when Beyfortus was given for fewer months. And that compressed window of use is itself telling: Beyfortus is not a traditional vaccine but a monoclonal antibody that wanes after five to six months, which is why it is administered only during RSV season (October–March).

In other words, all 37 deaths reported so far have clustered within less than two full seasons of use – a concentration that makes the disproportion even harder to dismiss.

Moreover, not only is the absolute number of reported infant deaths rising, but so is the proportion of reported deaths among total adverse event reports. As shown in Figure 1:

• In 2023, FAERS recorded 2 infant deaths among 122 reports (1.6%);
• In 2024, 15 deaths out of 352 reports (4.3%);
• And by September 2025, 20 deaths among 538 reports (3.7%) – despite the fact that the 2025-2026 RSV season had not yet begun.

The elevated proportions of death reports observed in 2024 and 2025 appear notably higher than historical VAERS patterns for this age group, raising concern that the trend may not merely reflect increased reporting volume, but could signal a product‑specific safety issue that requires further scrutiny.

The pattern of concern extends beyond US borders. Independent real-world data from France suggest a striking temporal association between the timing of the nationwide nirsevimab rollout and neonatal mortality patterns. During the autumn of 2023, as nirsevimab became widely available, France recorded statistically significant spikes in deaths among infants aged 2–6 days: 55 deaths in September and 62 in October. In November, when distribution was temporarily restricted, mortality dropped sharply to 26. As access resumed, deaths rose again – reaching 50 in December and 52 in January. While these figures do not establish causality, the recurring pattern aligned with availability underscores the urgent need for international pharmacovigilance and full transparency from both regulators and manufacturers.

Clinical Trials and Real-World Data Tell the Same Story

The consistency is striking. The same imbalance that first appeared in the trials – where infant deaths in the treatment arms were roughly double those in the control groups – is now echoed in real-world surveillance. In both settings, the signal is not diffuse or ambiguous, but concentrated and measurable. The trials showed a disproportionate mortality burden in the very populations meant to benefit; FAERS now shows that once the product was rolled out broadly, the pattern persisted. Taken together, these two lines of evidence form a coherent warning – one that regulators and advisory committees chose not to confront.

This failure to address a consistent and measurable safety signal is particularly troubling in light of how the review process unfolded. This should have been the moment for full transparency, especially given that ACIP was the sole remaining body tasked with reviewing safety. When Merck’s clesrovimab was submitted for approval, it bypassed FDA’s safety advisory committee (VRBPAC). In its approval documents, the FDA justified this decision by noting that clesrovimab was “not the first in its class,” and therefore did not require an additional advisory review. That left ACIP as the final institutional checkpoint before national rollout.

Yet rather than receiving the full picture, the committee was shielded from critical safety data – both the mortality imbalance in the trials and the emerging real-world signal. Advisory bodies cannot be expected to make evidence-based decisions when critical safety data is withheld from their review. When 37 infant deaths occur within fewer than two seasons of use – on top of the doubling in the number of deaths in the intervention group compared to control in the clinical trials – the public deserves answers, not silence. Anything less than full transparency, and a willingness to confront these safety signals directly, constitutes a failure of both scientific integrity and the duty to protect the very infants this product was intended to serve.

In light of the accumulating red flags, omissions, and suppressed signals now coming to light, it is no longer tenable for either product to remain shielded from full scrutiny. Both nirsevimab (Beyfortus) and clesrovimab warrant a thorough re-evaluation by ACIP – this time with complete data on the table. 

Withheld: Real-World Infant Deaths from RSV Antibody Shot
by Yaffa Shir-Raz at Brownstone Institute – Daily Economics, Policy, Public Health, Society