- Health
The human metapneumovirus (hMPV) has been circulating for decades and isn’t a side effect of the Pfizer-BioNTech COVID-19 vaccine
Key takeaway
Human metapneumovirus (hMPV) is a virus that infects the upper respiratory tract and causes common colds. In vulnerable groups, such as young children, the elderly, or immunosuppressed individuals, it can occasionally lead to complications like pneumonia. hMPV has been circulating for decades, and there is no data that establishes a causal relationship between hMPV infections and COVID-19 vaccines.
Reviewed content
Verdict:
Claim:
“Pfizer has disclosed that Human Metapneumovirus is one of the potential side effects of their mRNA vaccine”
Verdict detail
Misleading: Human metapneumovirus (hMPV) infection is listed in a Pfizer document as an adverse event following vaccination, not as a confirmed side effect. Adverse events are occurrences that follow vaccination but lack evidence of a causal link to the vaccine. By conflating these terms, the claim misleads readers into assuming causation where none has been established.
Inadequate support: Cases of hMPV are on the rise during the winter months of 2024 and 2025 in the Northern Hemisphere, as is common with many respiratory viruses at that period. However, the number of cases isn’t higher than expected for this time of the year and is lower than the number of cases prior to the rollout of COVID-19 vaccines in the U.S. Thus, there is no data supporting the claim of a vaccine-caused surge in hMPV infections.
Full Claim
“In a report, Pfizer has disclosed that Human Metapneumovirus is one of the potential side effects of their mRNA vaccine”
Review
In January 2025, a claim began circulating online that Pfizer had “disclosed” human metapneumovirus (hMPV) infections as a side effect of the Pfizer-BioNTech COVID-19 vaccine. Human metapneumovirus is a respiratory virus that causes symptoms similar to the common cold. However, it can cause more severe disease like pneumonia in vulnerable individuals, such as young children, older people, and immunosuppressed patients.
It gained attention in early 2025 due to a reported increase in cases in several countries. The outbreak was the subject of disinformation, some baselessly claiming that the virus was new and that China had declared a state of emergency.
However, the claim has no basis in facts. We’ll explain why below.
The claim originates from a misunderstanding of a Pfizer report submitted to the U.S. Food and Drug Administration (FDA) in 2021, which we examined in a prior review.
This document included a list of adverse events reported in the first three months following the rollout of COVID-19 vaccines. But it’s important to note that adverse events are not synonymous with side effects. While side effects imply a proven causal link to the vaccine, adverse events do not.
Indeed, the European Medicines Agency (EMA) defined adverse events as:
“Any untoward medical occurrence in a patient or clinical investigation subject administered a pharmaceutical product and which does not necessarily have to have a causal relationship with this treatment.” [our emphasis]
As we explained in our previous review, adverse events are medical conditions observed among vaccinated individuals that may or may not be caused by the vaccine. Thus, it’s inaccurate to claim that Pfizer labeled hMPV as a side effect of its COVID-19 vaccines.
Furthermore, there is no plausible mechanism connecting COVID-19 vaccines to hMPV.
hMPV isn’t a new virus; it was first identified in 2001, and genetic analysis has traced its presence back to the 1950s[1]. Like other respiratory viruses, such as influenza, hMPV cases typically surge during the winter months and is mostly transmitted through respiratory droplets or touching contaminated surfaces.
If hMPV were a side effect of COVID-19 vaccines, an unprecedented and progressive increase in hMPV cases would be expected, given the widespread global vaccination against COVID-19. However, available data suggest otherwise.
Paul Hunter, a professor of medicine at the University of East Anglia, noted that prevalence of hMPV in both the UK and in China was within the expected range for winter.
Similarly, data from the U.S. Centers for Disease Control and Prevention (CDC) showed that the percentage of hMPV test samples positive for hMPV during the years following the COVID-19 vaccine rollout was in the same ballpark as that of the 2019-2020 winter, before the COVID-19 pandemic and vaccine rollout. The positivity peaked at 7.09% in 2019-2020 and ranged between 7.77% and 10.99% from 2021 to 2024. The positivity is lowest during the 2024-2025 so far, at around 2%. Therefore, the epidemiological observations don’t support the allegation that COVID-19 vaccines can cause hMPV infection.
REFERENCES
- 1 – van den Hoogen et al. (2001) A newly discovered human pneumovirus isolated from young children with respiratory tract disease. Nature medicine.
