A study from the U.S. Centers for Disease Control and Prevention (CDC) found that children who received an original COVID-19 vaccine have little protection against hospitalization for the virus.

Upon receiving the vaccine, children had 52% protection against hospitalization, but after just four months, the vaccine’s efficacy dropped to 19%.

Protection against alleged critical illness also dropped in the months following inoculation, from 57% to 25%.

The study involved children aged 5-18 who received two or more doses of the original Pfizer-BioNTech or Moderna COVID-19 vaccines between December 19, 2021, and October 29, 2023.

The CDC concluded its study by calling for “up to date” vaccinations.

“To address low coverage of updated vaccines and waning effectiveness of the original monovalent vaccine, children and adolescents should remain up to date with COVID-19 vaccination, including the current CDC recommendation for all persons aged ≥6 months to receive vaccination with updated (2023–2024) COVID-19 vaccines,” the researchers wrote.

Another study found that toddlers and young children have a greater risk of seizing after receiving the COVID-19 vaccine.

Researchers from the U.S. Food and Drug Administration (FDA) admitted in a preprint paper that the risk of seizure was “significantly elevated.”

Within 24 hours of receiving the Moderna vaccine, children had a 2.5 greater chance of experiencing a febrile seizure. The incidence of seizures was greater during that period than in children 8-63 days after vaccination.

The paper noted that the “risk interval of 0-1 days” ensures that “febrile cases are more likely to be associated with vaccination rather than other causes.”

Despite the “significantly elevated” risk the COVID-19 vaccine presents in toddlers, the FDA concluded that the “safety profile of the monovalent mRNA vaccines remains favorable for use in young children.”

The Moderna and Pfizer-BioNTech vaccines for those aged 12 and older have also been linked to anaphylactic reactions, lymphadenopathy, and appendicitis, according to a Norwegian study.