YouTuber misinterprets Covid-19 vaccine evidence on children from Singapore

A video watched more than 700,000 times on YouTube, and being shared on Facebook, wrongly claims that a new study in the New England Journal of Medicine (NEJM) means that “the risk of adverse events [from vaccination] is roughly a little more than four times greater than the risk of the child requiring oxygenation [from Covid-19]”.

The video was posted by a popular YouTuber called Dr John Campbell, who regularly posts videos about Covid, and whose YouTube channel has been watched more than half a billion times.

At the end of the video, Dr Campbell invites viewers to “see if I have misinterpreted anything”.

He has, in several ways.

The study shows that the vaccines protected children against hospitalisation with Covid, and does not show that the risk of serious adverse reactions to the vaccine was greater than the risk of getting seriously ill with the disease.

What is the study all about?

The study used data from Singapore in the early months of 2022, when Omicron was the dominant Covid-19 variant, to assess the effectiveness of the Pfizer Covid-19 vaccine in about a quarter of a million children aged 5 to 11.

Among these children, about 200,000 were fully (two doses) or partially vaccinated during the study period (21 January to 8 April), and about 50,000 were not vaccinated.

Up until the end of February (so about half way through the study period), 22 serious adverse events following vaccination were reported within the group, corresponding to 0.005% of doses—although the Singaporean document carrying this data, and which the study links to, says that a reported adverse reaction “does not necessarily have a causal relationship with this treatment/vaccination”.

During the whole study period, there were also a total of 288 hospitalisations with Covid—whether among vaccinated or unvaccinated children—five of which involved the children needing oxygen treatment.

The study estimated that fully vaccinated children were about 83% less likely to be admitted to hospital with Covid than unvaccinated children, and partially vaccinated children were also protected, but to a lesser extent.

What the video got wrong

In his video, Dr Campbell agrees that the study shows that the vaccines significantly protected children against being hospitalised with Covid.

He does a different analysis, however. Instead of comparing the number of Covid hospitalisations among vaccinated and unvaccinated children, he compares the number of serious Covid hospitalisations by his own definition (five, who received oxygen treatment) with the number of adverse events reported following vaccination (22), thereby seeming to suggest that the risk of vaccination may outweigh the risk of Covid-19 to children.

But this is seriously flawed, in several ways.

Firstly, the total number of children seriously ill in hospital with Covid doesn’t measure the underlying risk of the disease to them, because about four fifths of the children in the study had already been protected by the vaccine—meaning some of them may otherwise have caught Covid and got seriously ill, but didn’t.

If Dr Campbell wanted to measure the risks of Covid for people who aren’t vaccinated, he should have looked at the rate of hospitalisation among unvaccinated children only. Or, like the UK Health Security Agency (UKHSA) or the Joint Committee for Vaccination and Immunisation (JCVI) looked at the benefits of vaccination in terms of hospitalisations prevented.

In any case, Dr Campbell does not count the total number of hospitalisations with Covid (288). He counts only the hospitalisations that needed oxygen treatment (five), with the justification that he believes “a lot are being admitted on a precautionary basis”.

However the study itself does not say that the other 283 admissions were non-serious or “precautionary” cases.

What about the risks of vaccination itself?

Despite excluding 283 of the 288 hospital admissions on the assumption that many may be “precautionary” cases, Dr Campbell includes all 22 serious adverse events reported following vaccination when considering the risk from the vaccines.

He does this despite not knowing whether these adverse events were as serious as the cases of children needing supplemental oxygen, or whether they were even caused by the vaccine.

The events are described by the Singapore Health Sciences Authority (HSA) in a document cited in the original study. This document explains that an adverse event is classified “serious” when “the event resulted in hospitalisation/extended stay in hospital, resulted in a significant reduction in functioning level/disability, resulted in a life-threatening illness (e.g. anaphylaxis) or death, resulted in birth defects or is a medically important event”.

It is therefore possible that some of the 22 events Dr Campbell mentions “resulted in hospitalisation”, but were in fact less serious than some of the 283 hospital admissions with Covid that he disregards.

Dr Campbell also incorrectly suggests that these serious events were caused by the vaccines, including when he describes them as a “reaction to vaccine” in the video note.

The same HSA document says: “It is important to note that the [adverse events] reported do not necessarily mean that the vaccine has caused these [adverse events] as they may be related to an underlying or undiagnosed disease or the natural progression of an underlying disease. It may be coincidental that the event occurred around the same time when the vaccine was given but is not caused by the vaccine.”

Dr Campbell does not mention this.

How long does protection last?

Dr Campbell talks about doing a risk benefit analysis with the data in this study, but a large part of the benefit of the vaccines is not included, because we know that the Covid vaccines continue to protect against hospitalisation with the disease for months at least.

According to UKHSA estimates, the Pfizer vaccine still offers around 85% protection, even with Omicron, after 4-6 months. Much of the benefit of being vaccinated therefore wouldn’t be captured by this study, which only looked at a period of two and a half months.

Any adverse events from vaccination, on the other hand, usually occur within six weeks.

The data on adverse events is potentially also incomplete, because the study only included adverse events reported following vaccination up to 28 February, not until the end of the study period.

In short, Dr Campbell may sound as though he is comparing the risk of the Covid vaccine to the risk of Covid itself, but his analysis:

• includes serious adverse events that the vaccine may not have caused
• excludes many Covid hospitalisations that may have been more serious than those events
• excludes many Covid hospitalisations that would have occurred if most of the children in the study had not been vaccinated
• excludes much of the benefit (and potentially some of the risk) of vaccination

Full Fact approached Dr Campbell for comment but had not received a response at the time of publication.

The benefits of vaccination do outweigh the risks

The risks to children, both from Covid and from Covid vaccines, are very low. They are also hard to estimate precisely.

When assessing the evidence for healthy 5-11-year-olds in February, the Joint Committee on Vaccination and Immunisation said the benefits of vaccination were uncertain because they would depend on the size of future waves of Covid and the characteristics of future variants.

 “Overall,” it said, “the committee agreed that the potential health benefits of vaccination are greater than the potential health risks”.

Image courtesy of Braňo