Covid-19 severity mirrors influenza as vaccine development lags

Prof Yong Poovorawan, head of the Centre of Excellence in Clinical Virology at the Faculty of Medicine, Chulalongkorn University, has highlighted the continuing challenge of developing vaccines quickly enough to keep pace with rapidly evolving viruses.

In a post on his personal Facebook account on Monday (September 7), Yong wrote that vaccine development inevitably trails viral evolution, particularly in the case of RNA viruses, which change continuously and relatively quickly.

Current approaches to Covid-19 and influenza vaccines remain largely focused on catching up rather than staying ahead, he explained. Vaccine strains are selected according to viruses already circulating, together with predictions about which strains are likely to spread in the months ahead.

Yong identified RK.1 as the Covid-19 variant currently circulating in Thailand, describing it as a descendant of NB.1.8.1, which spread last year. Vaccines currently authorised for use in the United States are based on XFG, which belongs to a different branch from the lineage circulating in Thailand, he noted. The Thai lineage is itself a later descendant of JN.1.

One of the main obstacles is the production timeline. Developing and manufacturing an updated vaccine typically takes about three to six months, meaning the virus can continue evolving before the vaccine reaches people.

This leaves vaccine developers in what Yong described as a continuing race to catch up with viral change. He argued that the longer-term goal should instead be a broadly protective vaccine capable of covering past, present and future variants of the same virus — an approach he referred to as “one for all”.

Reaching that goal, he wrote, may depend on a new generation of scientists willing to pursue ideas that differ from conventional vaccine-development methods and to think beyond established approaches.

In an earlier Facebook post, Yong also examined this year’s Covid-19 outbreak pattern, which he described as markedly different from the previous two years.

In recent years, Covid-19 infections in Thailand have generally begun rising after the Songkran festival, continued through the rainy season and started to decline from August. This year, however, infections remained comparatively low during the first part of the year before increasing over the past two months.

The outbreak is still at its peak, according to Yong, who expects infections to begin falling in October, coinciding with the school break.

He also observed that the seasonal pattern of Covid-19 is becoming increasingly similar to that of influenza. Influenza cases rose early this year during the cool season before increasing again over the past two months, slightly later than usual, bringing the two diseases into broadly the same seasonal period.

Influenza infections have nevertheless been far more numerous, with the total number of reported cases about three times that of Covid-19.

On severity, Yong pointed to the proportion of deaths among reported cases. He cited 16 Covid-19 deaths among about 100,000 cases, compared with around 50 influenza deaths among 350,000 cases.

Based on those figures, he concluded that the case-fatality rates of the two diseases are now at broadly comparable levels and that, by this measure, Covid-19 is no longer more severe than influenza.