In the study co-led by Professor Yuen Kwok-yung, one dose of a Covid-19 vaccine was administered separately to three different hamsters before, after and on the day that they were exposed to the coronavirus.

The experimental design was meant to simulate health conditions in people who are exposed to the coronavirus around the time of vaccine administration, as people may be worried about whether it is too late to get vaccinated, and whether side effects may exacerbate Covid symptoms.

The study found that all the vaccinated hamsters had significantly lower disease severity score, body weight loss, lung damage, and higher antibody count when compared to the unvaccinated control group.

These improvements were the most noticeable in the hamsters who received the vaccine before they were exposed to the virus, whereas the others, including the hamsters that were vaccinated after contracting the virus, also experienced less severe symptoms.

The results of the study suggest that vaccination before or soon after exposure to Covid-19 mitigates rather than worsens symptoms. Fully vaccinated adults and children will only develop mild symptoms even if infected. The priority is to get all eligible people in Hong Kong vaccinated as soon as possible.

“If you have unvaccinated young children, elderly or people with chronic illness at home, try to get antigen tests for everyone for alternate day testing,” Yuen advised.

He also recommends double masking with an outer cloth mask and an inner surgical mask to minimize any potential virus exposure, especially to children or the elderly.