Dr. Wee et al. reported in JAMA Pediatrics that study results suggest that completion of a primary mRNA vaccine series provided protection against SARS-CoV-2 infection in children aged 1 through 4 years. Furthermore, Dr. Wee et al. also reported that there is potential benefit of vaccination in preventing infection and potential sequelae.

In Japan, from September 20, 2023, an mRNA-based COVID-19 monovalent vaccine (Pfizer/BionTech) compatible with the omicron type SARS-CoV-2 XBB.1.5 variant has been available to all people over 6 months of age. Officials of Japan's Ministry of Health, Labor and Welfare reported that the pain at the injection site, fatigue, headache, joint or muscle pain, chills, fever, etc. are observed as the main side reactions in people of all ages who have been vaccinated against the SRAS-CoV-2 XBB.1.5 variant. Additionally, arthralgia (approximately 5%) has been observed in children aged 6 months to 4 years who have been vaccinated against the XBB.1.5 variant. In Japan, the total number of moderate to severe cases of COVID-19 up to the age of 4 years is approximately 58% of the total number of moderate to severe cases of COVID-19 under the age of 20 years. Acute encephalopathy, pneumonia, and convulsions were observed in many cases of moderate to severe cases of COVID-19 up to the age of 4 years. However, in Japan, the number of children aged 6 months to 4 years who have been vaccinated with mRNA-based COVID-19 vaccines is approximately 4% of the total population of children aged 6 months to 4 years. Therefore, in Japan, vaccination against the XBB.1.5 variant is recommended for infants aged 6 months to 4 years.

The report on the results of the clinical trial by Dr. Wee et al. is expected to contribute to the widespread use of vaccines against the XBB.1.5 variant for infants aged 6 months to 4 years in Japan.

We do not have potential conflicts of interest.

NHO Kyoto Medical Center                                                                        Cancer Genome Medicine, Kyoto University Hospital

Doctor specializing in Cancer Genome Medicine                                      Doctor specializing in emerging infectious diseases

Published in JAMA Pediatrics on October 17, 2023. by Kyoto@takumaH