Infants younger than 6 months had the second highest COVID-associated hospitalization rate for most of the pandemic

A post published on Facebook in February 2025 claimed that babies younger than 6 months had “the second highest [COVID-19] hospitalization rate after the elderly”.

Children in general notoriously fare better than adults and older people against COVID-19. So the claim that some categories of children have a high rate of COVID-associated hospitalization might legitimately sound surprising.

To better understand the reality of the situation, we analyzed data from the U.S. COVID-NET network. COVID-NET collects data from a network of hospitals across ten U.S. states covering about 34 million people. It keeps track of the rate of COVID-associated hospitalizations, which the network defines as “laboratory-confirmed SARS-CoV-2 in a person who lives in a defined COVID-NET surveillance area and test[s] positive for SARS-CoV-2 within 14 days before or during hospitalization”.

We analyzed the weekly rate of COVID-associated hospitalization, expressed as the number of COVID-associated hospitalizations per 100,000 persons, for each age group from march 2020 to December 2024. Over the entire time period, the below 6 months age group had, on average, a COVID-associated hospitalization rate of 9.7. This is indeed second to the “above 75 years” age group (Figure 1).

The data averaged over the entire time period does support the claim. However, a detailed analysis offers a more nuanced view. For each week from March 2020 to December 2024, we ranked the age groups according to their hospitalization rate. The “younger than 6 months” age group had the second highest hospitalization rate for 58% of the weeks (Figure 2). The rest of the time, this age group ranked mostly third and fourth for hospitalization rate.

Thus, babies younger than 6 months weren’t always the age group with the second highest rate of COVID-associated hospitalization.

We also looked at the evolution of the hospitalization rate over time (Figure 3). We observed a clear change in the hospitalization rate at the end of December 2021. Before that date, children below 6 months ranked third or fourth for hospitalization rate, below the 50-64 and above the 75 year age groups. The situation changed at the end of 2021 and the beginning of 2022, when children under 6 months began ranking second for hospitalization almost consistently.

Other studies confirmed that the hospitalization rate of babies younger than 6 months increased at the beginning of 2022, corresponding to the emergence of the Omicron variant[1]. Possible explanations for that phenomenon are the increased transmissibility of Omicron combined with the fact that babies below 6 months aren’t eligible for vaccination, contrary to other age groups. However, maternal vaccination during pregnancy is able to provide some protection to newborns during the first months of life.

In summary, it’s accurate that, on average, babies younger than 6 months are the second-most susceptible age group to COVID-associated hospitalization, behind elderly people above the age of 75. This hasn’t always been the case, though. Indeed, the hospitalization rate of this age group was lower during the first two years of the pandemic and began to surge in early 2022, when the Omicron variant emerged and other age groups began to receive vaccinations. Because babies younger than 6 months aren’t eligible for vaccination, it poses an increased risk for this group to contract the virus and, in severe cases, to be hospitalized.

REFERENCES

• 1 – Hamid et al. (2022) COVID-19–Associated Hospitalizations Among U.S. Infants Aged <6 Months — COVID-NET, 13 States, June 2021–August 2022. Morbidity and mortality weekly report.