PHILADELPHIA — Simultaneous administration of childhood vaccines against up to eight pathogens at one time did not result in any major adverse events or any greater side effects than a six-valent vaccine on its own, according to a poster presented at the annual meeting of the American Academy of Allergy, Asthma and Immunology 2026 Annual Meeting in Philadelphia.

“The simultaneous administration of vaccines against different pathogens during one visit to a medical facility is safe and contributes to maintaining optimal clinical benefits with maximum protection of the child,” concluded Anastasiia Bondarenko, PhD, MD, DSc, professor of medicine and head of the Department of Pediatrics, Immunology, Infectious and Rare Diseases of the European Medical School at the International European University in Kyiv, Ukraine, and her colleagues.

The expansion in vaccines available to protect children against infectious disease has been accompanied in recent years by growing concerns from some families about the safety of giving children multiple vaccines at one time. To understand whether reactions differed by the number of vaccines given, the researchers assessed postvaccination effects in four groups receiving varying numbers of vaccines.

The study enrolled 460 children, aged 2-18 months, from January 2020 to October 2023 at a Kyiv outpatient center. One group of 115 children received only the single-injection hexavalent vaccine against pertussis, diphtheria, tetanus, polio, hepatitis B, and Haemophilus influenzae type b (Hib). Another group of 115 the received the hexavalent vaccine with the rotavirus vaccine, and another 115 children received the hexavalent vaccine with the pneumococcal vaccine. The final group of 115 received the hexavalent vaccine plus the rotavirus and pneumococcal vaccines.

Among the children receiving only the hexavalent vaccine by itself, 60% had no complaint, compared to 93% of those receiving the hexavalent and pneumococcal vaccines, 85% of those receiving the hexavalent and rotavirus vaccines, and 75% of those receiving the hexavalent, rotavirus, and pneumococcal vaccines. 

A third of the children (32%) receiving the hexavalent vaccine had a fever above 37 °C, compared to 5% receiving the hexavalent and pneumococcal vaccines, 12% receiving the hexavalent and rotavirus vaccines, and 25% of those receiving the hexavalent, pneumococcal, and rotavirus vaccines.

Injection-site pain occurred in 2% of the children receiving the hexavalent and pneumococcal vaccines and in 3% of those receiving the hexavalent and rotavirus vaccines. Among those receiving only the hexavalent vaccine, 4% also reported general discomfort and 4% had moodiness, neither of which was reported in any of the other groups. None of the differences between the groups for any reactions were statistically significant.

The findings were not surprising to Eve Switzer, MD, general pediatrician at Northwest Pediatrics in Enid, Oklahoma, who reviewed the results.

“This study reinforces what pediatricians have known for years — giving recommended vaccines together is safe, well tolerated, and helps protect infants as early as possible without increasing significant side effects,” Switzer, told Medscape Medical News. “There are a few gaps in the study, so it’s not definitive, but it’s definitely supportive of what we’ve always known.”

The vaccines in the study are all universally recommended by the American Academy of Pediatrics.

The study was funded by Allergy Therapeutics PLC. The authors did not report any disclosures. Switzer had no disclosures. 

Tara Haelle is a science/health journalist based in Dallas.