How to protect yourself against seasonal coronavirus

Writing on Facebook, Yong said Covid-19 has become a seasonal disease, similar to other respiratory infections including flu, RSV, and rhinovirus.

He said these seasonal bugs can cause problems, especially for vulnerable groups, such as the elderly, those with weak immunity, people with underlying diseases, and young children.

Just as flu vaccine shots do not prevent infection with influenza, which continues to spread with new strains every year, Covid shots are not a guaranteed defence against coronavirus, Dr Yong added.

However, vaccination and/or previous infection should reduce the severity of symptoms. In general, the severity of symptoms after catching Covid-19 for the second and third time decreases, except among vulnerable people, Yong said.

This is similar to Respiratory Syncytial Virus (RSV), which usually causes cold-like symptoms in young children. The symptoms become milder if the child is reinfected again a few years later, he added.

Seasonal respiratory diseases can strike any time of the year, but often peak during the wet season from late May to September, Dr Yong said.

Respiratory diseases, whether it's influenza, RSV, or Covid-19, all mutate to evade the immune system and thereby cause reinfection. However, symptoms of infection may be reduced or even absent in healthy people with strong immunity.

Maintaining good health and proper hygiene, as well as getting annual flu and Covid boosters can help reduce chances of getting infected by respiratory diseases, Yong said.

However, there is still no effective vaccine for RSV despite many years of testing, he added.