Local expert concerned with side effects of diluted vaccine for young children aged 6 months old and above

Professor Yu-lung Lau

2nd August 2022 – (Hong Kong) The COVID-19 epidemic situation in Hong Kong is still severe, and young children have been infected recently. A 22-month-old baby girl passed away recently. After an online meeting yesterday,  the Scientific Committee on Vaccine Preventable Diseases and the Scientific Committee on Emerging and Zoonotic Diseases (JSC) under the Centre for Health Protection (CHP) of the Department of Health, joined by the Chief Executive’s expert advisory panel (EAP) unanimously agreed to lower the minimum age for vaccination against COVID-19 from 3 years old to 6 months old.

Meanwhile, Professor Yu-lung Lau, Chairman of the Scientific Committee on Vaccine Preventable Diseases said during a radio interview today that with reference to the fifth wave of epidemic data, there will be cases of critical or death cases of infected young children from time to time. Parents are advised to vaccinate young children as soon as possible before more mutated strains emerge.

Lau said that the dose of the CoronaVac vaccine by Sinovac for young children is the same as that for adults, while the Comirnaty vaccine has a 3-µg dose as a three dose series. The 3-µg dose was carefully selected as the preferred dose for children less than 5 years of age based on safety, tolerability, and immunogenicity data.

Pfizer and BioNTech submitted the same data to the U.S. Food and Drug Administration (FDA) which granted emergency use authorisation (EUA) of the Pfizer-BioNTech COVID-19 vaccine as a three 3-µg dose series in this age group on 17th June. The companies also plan to submit these data to other regulatory agencies around the world. 

It is recommended that the government strive to purchase these vaccines. The Comirnaty vaccine is formulated to the appropriate dose for young children, but the practice of dilution is unprecedented in the world. If there is an error, it may impact its effectiveness or increase the side effects. However, it is not completely unfeasible and so, the vaccine needs to be carefully studied by experts. As for some parents who are concerned about the risk of myocarditis caused by the vaccination of young children, Lau pointed out that the 8-week interval of vaccinating two doses of Comirnaty in young children is a compromise, and it is believed that the risk can be reduced.

He also pointed out that at present, high-risk workers over the age of 18 can choose to receive the fourth dose of vaccination. At present, 75% of the 50-59-year-old group are vaccinated with the third dose, but there are still some severe cases and deaths. Many persons in the relevant age group have underlying diseases. It is recommended that the government encourages people over 50 to get the fourth shot, but it is not mandatory.