Letters | Could vaccine and catching Omicron be key to Hong Kong’s immunity?

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Research suggests that immunity against Covid-19 can be acquired from catching the infection naturally, and the resultant immunity can be even better if the infection is acquired while vaccination-induced protection is still in strength. According to one study, this resultant “hybrid immunity”, a combination of vaccine- and infection-induced immunity, when measured in level of humoral antibodies, can be higher than that from the vaccine alone.

Like the rest of the world, Hong Kong is unable to stop the spread of the Omicron variant. This could be an opportune moment for Hongkongers to contract an Omicron infection to acquire hybrid immunity through a rapid, structured dropping of all anti-pandemic measures. Waiting longer will result in vaccine-acquired immunity in the community waning, resulting in less effective hybrid immunity and more severe illness.

For the fully vaccinated, the offer of hybrid immunity gained from Omicron’s milder illness is preferable to interminable social disruption. Adults who are not yet fully vaccinated are surely aware of the risk from their freedom of choice. Meanwhile, there are now oral antiviral drugs to help the old and infirm mitigate against progression to serious illness.

Most unvaccinated children are below three years old, and for them Omicron continues unabated as a novel virus. Fortunately, Omicron in this age group tends to present as an upper respiratory tract illness with fever and croup, which respond well to treatment. The reason more children are being admitted to hospital is because there is a huge number of infected children, not because the Omicron is more virulent than the Delta variant.