CDC analysis of RSV vaccines data showed vaccines are safe, not associated with excess deaths, contrary to claim by Children’s Health Defense

In 2023, the U.S. Food and Drug Administration (FDA) approved several treatments to protect young children and older adults from infections with the Respiratory Syncytial Virus (RSV).

In May of that year, the agency approved two RSV vaccines for use in adults above 60: one from GSK (Arexvy) and one from Pfizer (Abrysvo).

The FDA also approved a monoclonal antibody, nirsevimab (commercialized as Beyfortus) for use in children up to 24 months, and extended Abrysvo’s approval to pregnant women within 32 to 36 weeks of pregnancy. Vaccination of pregnant women aimed to provide the babies with immunity to RSV during their first months of life.

Several months later, Children’s Health Defense (CHD), an association known for disseminating anti-vaccine disinformation, published an article implying that these treatments were dangerous and should be pulled from the market. However, their interpretation of publicly available safety data on RSV vaccines is misleading, as we explain below.

RSV infections are mostly mild, but the virus is a public health issue

CHD’s article cast doubt on the need to prevent RSV infections, arguing that RSV is only responsible for mild cold-like symptoms. To support this claim, the article included quotes from Meryl Nass and Peter McCullough, both of whom previously shared medical falsehoods. “Why would anyone take an RSV vaccine that has a reasonable chance of causing a neurologic illness to prevent colds?” said Nass. McCullough claimed that RSV “is like a mild cold and easily treated at home.”

However, this is an incomplete and misleading picture of the disease. RSV is a common respiratory virus mostly circulating during winter, along with other respiratory viruses like the flu. Most people with RSV infection show classic cold-like symptoms like a runny nose, sneezing, and fever, and recover within one or two weeks.

However, complications can occur, where the infection progresses into lower respiratory tract infections, causing bronchiolitis and pneumonia. RSV infection leads to 2.1 million outpatients visiting the hospital each year. It causes 60,000 to 120,000 hospitalizations and 6,000 to 10,000 deaths each year among adults above 65. For children under five, the virus is responsible for 58,000 to 80,000 hospitalizations and 100 to 300 deaths annually.

According to the U.S. Centers for Disease Control and Prevention (CDC), RSV infection is the most common cause of hospitalization of young children.

Additionally, a surveillance study monitoring 600 young children in need of intensive care because of RSV found that the majority of them were “delivered full-term and previously healthy”^[1]. Since most children get infected by RSV in their early years, this means that even parents of healthy children should consider the risk that their child may suffer from RSV complications.

Apart from the risk of the disease posed to individuals, RSV can also pose a threat to the community at large through its impact on the functioning of the healthcare system.

Indeed, news articles reported that people seeking medical attention in the post-COVID era because of RSV complications in winter strained hospitals’ capacity and may divert resources from other important needs. In other words, failing to implement protective measures, including vaccination, on a preventable disease may not only expose people to risk of complications from the disease, but may also hinder the proper function of the healthcare system.

Thus, the CHD’s implication that vaccinating against RSV is unnecessary because the virus only causes the common cold provides the reader with a misleading picture of the public health threat posed by RSV.

VAERS reports alone don’t provide sufficient evidence to conclude that a vaccine is dangerous

The CHD article claimed that the Vaccine Adverse Events Reporting System (VAERS) “already show reports of 34 deaths, 302 serious adverse events and according to news reports this week, a safety signal for Guillain-Barré syndrome (GBS) [a neurological condition” even though it had been “less than a year” since the vaccines’ approval.

From these figures, the CHD article concluded that the RSV vaccines had “been linked to deaths and serious injuries” and that “experts” said that “it’s time to pull [the vaccines] from the market”.

Misusing VAERS data is a common method of producing vaccine misinformation, as previous reviews from Science Feedback have documented. CHD repeated this same mistake in their article.

VAERS is a database co-managed by the CDC and FDA where anyone can submit reports of adverse events occurring after vaccination. By casting a wide net for vaccine adverse events, VAERS is designed to assist in detecting rare vaccine side effects that go unnoticed during clinical trials and to monitor unexpected increases in specific adverse events that might indicate a problem with safety.

For example, several cases of intussusception in children who just had received a rotavirus vaccine were reported to VAERS in 1998 and 1999. The unexpected number of VAERS reports prompted the CDC to carry out a more in-depth investigation to validate the reports and to assess the risk. The investigation eventually led to the vaccination recommendation being suspended and the vaccine being recalled.

VAERS can also help detect possible human errors. For example, it is accurate that some young children received RSV vaccines even though this product isn’t FDA-approved for them. This prompted the CDC to issue a communication and recommendations to healthcare providers which incorrectly administered the vaccines.

However, VAERS reports need to be combined with additional investigations, such as statistical analyses and clinical follow-ups of affected people, to be useful in detecting side effects and problems with vaccine safety. On their own, VAERS data is insufficient for forming reliable conclusions on vaccine safety and the relationship between a vaccine and an adverse event.

First, the fact that one event occurs after another doesn’t mean that one caused the other. Assuming the opposite without any further information is known as the post hoc ergo propter hoc fallacy.

For instance, it’s possible for an individual who experienced an adverse event following vaccination to have also received another medical intervention that caused the adverse event. Concluding that the vaccine caused the adverse event solely on the grounds the individual got vaccinated previously, without considering their entire medical history, is flawed reasoning.

Second, the fact that anyone can submit a report, including the general public that largely has little to no medical training, means that there is no way to guarantee that submitted information is complete or even accurate.

The disclaimer on the VAERS webpage warns of the same limitation:

“VAERS reports may contain information that is incomplete, inaccurate, coincidental, or unverifiable. Reports to VAERS can also be biased. As a result, there are limitations on how the data can be used scientifically.”

And:

“Anyone, including healthcare providers, vaccine manufacturers, and the public can submit reports to the system. While very important in monitoring vaccine safety, VAERS reports alone cannot be used to determine if a vaccine caused or contributed to an adverse event or illness.”

In addition, the disclaimer warned against using raw numbers of reports of a given adverse event such as death to establish causal associations, which is what CHD did in its article:

“The number of reports alone cannot be interpreted as evidence of a causal association between a vaccine and an adverse event, or as evidence about the existence, severity, frequency, or rates of problems associated with vaccines.”

These important caveats don’t mean that VAERS isn’t useful. But VAERS reports represent only the first step in determining whether an adverse event and a vaccine are linked. Researchers must perform further investigations starting with these reports to arrive at scientifically sound conclusions.

However, the number of deaths and serious adverse events reported to VAERS among people who received the RSV vaccines isn’t sufficient evidence of a causal association between the vaccine and the adverse event. Therefore, these numbers alone don’t support CHD’s claim that the RSV vaccines are dangerous or that they should be pulled from the market.

The CDC didn’t ignore safety signals

CHD also claimed that the CDC’s Advisory Committee on Immunization Practices (ACIP) “primarily focused on [Guillain-Barré Syndrome] safety signals, glossing over deaths and the administration of the vaccines to unauthorized age groups”.

Thus, the article implied that the ACIP, which is responsible for assessing the safety of vaccines and issuing vaccine recommendations, overlooked important safety signals related to the RSV vaccines that should have led to pulling them off the market.

However, this is inaccurate. First, the CDC acknowledged and acted upon the incorrect administration of vaccines to some people, as we explained in the previous section.

Second, the ACIP did look at the number of deaths among vaccinated individuals. The CDC presented data on the number of adverse events of special interest after RSV vaccination during the ACIP meeting on 28 February 2024, as shown in slide 22 of this presentation.

CHD was well aware of this presentation as it is explicitly referenced in their article. What CHD may have missed is that the CDC carried out a statistical analysis of the frequency of adverse event reporting, as mentioned in slide 15.

As we explained in the previous section, VAERS data need to be further analyzed in order to provide valid information on vaccine safety. The statistical analysis performed by the CDC aimed at detecting adverse events that showed up at an abnormally high rate.

According to slide 22, the CDC didn’t detect safety signals regarding deaths. Thus, the CDC didn’t “gloss” over the death reports, contrary to CHD’s claim. In fact, the CDC’s statistical analysis didn’t show that people were dying at a higher rate than expected in a normal population.

In contrast to deaths, the occurrence of Guillain-Barré Syndrome did raise a safety signal in the CDC’s statistical analysis. According to slide 22, the CDC only detected a signal for Guillain-Barré Syndrome among people who received the Abrysvo vaccine but not the Arexvy vaccine. According to slide 28 of the presentation, the observed rate of Guillain-Barré Syndrome in the 21 days after vaccination was 4.6 events per million Abrysvo doses administered, whereas the expected rate was two events per million doses.

However, the health and medicine news outlet STAT reported that it was too early to draw definitive conclusions owing to the small number of detected Guillain-Barré Syndrome cases. STAT also pointed out that several individuals had also received other vaccines, which makes it more difficult to draw a direct relationship between the RSV vaccine and the adverse events.

Citing CDC sources, STAT reported that, “between 2,400 and 2,700 RSV hospitalizations, 450 to 520 intensive care unit admissions, and 120 to 140 deaths are averted” for one million doses of RSV vaccine administered. As a result, the CDC concluded that the benefits still outweigh the potential risks and maintained its recommendation that adults over 60 get vaccinated against RSV.

Conclusion

The CDC’s statistical analysis didn’t show a higher-than-expected number of deaths among the population who received the RSV vaccines. By contrast, the CDC found a higher-than-expected number of cases of Guillain-Barré syndrome. However, the number of cases were small, hence there’s still not enough data yet to clearly establish a causal relationship between RSV vaccines and Guillain-Barré syndrome.

CHD’s claim that RSV vaccines are unsafe relied on the incorrect use of VAERS data, specifically by disregarding the fact that raw figures of adverse event reports cannot be used alone to establish a vaccine’s safety profile. The CHD article also misleadingly downplayed the public health threat of RSV infection, which causes over 100,000 hospitalizations each year, thus impacting the availability of hospital beds in winter.

REFERENCES

• 1 – Halasa et al. (2023) Infants Admitted to US Intensive Care Units for RSV Infection During the 2022 Seasonal Peak. JAMA Network Open.