S'pore infectious diseases experts sceptical about US study claiming Covid-19 reinfections more dangerous

Study might not be generalisable.

Belmont Lay | November 15, 2022, 07:03 PM

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Infectious diseases experts in Singapore are highly sceptical about the findings of an American study that supposedly found that people who are infected with Covid-19 more than once are at higher risk of organ failure and death.

The study concluded that patients with reinfections were twice as likely to die and three times more likely to be hospitalised than those infected for the first time.

The study, "Acute and postacute sequelae associated with SARS-CoV-2 reinfection", was published in the Nature Medicine journal on Nov. 10, 2022.

The retrospective study looked at nearly 41,000 Veterans Affairs (VA) patients who had two or more documented infections, and 444,000 who were infected for the first time, out of a 5.8 million total patient population.

It was conducted by the Washington University School of Medicine and the VA St Louis Health Care System.

The study relied on statistical modelling.

What local experts said

According to The Straits Times, local experts said the U.S. study's results are questionable, with inherent limitations and overstated conclusions.

Here's a list of their rebuttals:

Reinfected group appeared more sickly

The patients in the reinfected and first-time-infected groups had very different health profiles.

The reinfected group comprised patients who were three times more likely to be immunocompromised and nine times more likely to be in long-term care.

The absolute number who were reinfected -- 41,000 out of 5.8 million -- was also very small.

Local expert who pointed this out: Paul Tambyah, a professor and senior infectious diseases consultant at National University Hospital (NUH) and president-elect of the International Society for Infectious Diseases.

Data from Singapore different

Data derived from patients in Singapore showed different results from what was presented by the American study.

Over a month and a half -- from October 2022 to mid-November 2022 -- data from Singapore only showed a small percentage of people who suffered from severe illness, required oxygen, intensive care or died.

The figures stood at 0.2 per cent for patients previously infected, and 0.3 per cent for those getting an infection for the first time.

The U.S. study also focused more on older male patients, many of whom smoke or have serious medical problems.

As a result, the findings of the U.S. study may not apply to the general population.

Local expert who pointed this out: Shawn Vasoo, a clinical director at the National Centre for Infectious Diseases.

Not enough info on condition of those reinfected

Even though the study said those reinfected were 3.5 times more likely to develop lung problems and three times more likely to suffer heart conditions, there was very little information on what chronic diseases those cases who were reinfected had to begin with.

Local expert who pointed this out: Ooi Eng Eong, a professor and an expert in emerging infectious diseases at Duke-NUS Medical School in Singapore.

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