Don’t underestimate Covid in children

COMMENT: While policymakers around the world debate the costs and benefits of vaccinating children against Covid-19, in Aotearoa New Zealand we have an almost unique advantage of being able to weigh the evidence before making key decisions about how best to protect our children.

Optimal decision-making means we must neither over- nor underestimate the risks of Covid-19 infection in children. For that reason, it is concerning that inaccurate statements have been made recently by a member of the Covid-19 Plan B group of academics. These academics have previously criticised the Government’s Covid-19 elimination strategy by minimising the severity of the pandemic, and they now appear to be underestimating the impact of this infection in children.

In a recent opinion piece published by Newsroom, Ananish Chaudhuri, professor of experimental economics at the University of Auckland, criticised any future plans for vaccination of children, claiming:“Globally, very few children have contracted Covid-19 and therefore they are unlikely to pass it on. These children are being vaccinated not for their own health, but in order to protect other, mostly elderly, citizens.” The piece has since been amended to state that “the risk to children of severe illness or death from Covid-19 is minuscule”. These statements do not match up to current evidence.

Compared to adults, children and young people make up a lower proportion of Covid-19 infections. However, because children and young people comprise some one quarter to one fifth of the population, the actual numbers of infected children are high and rising. By May 2021, an estimated 12.2 million child cases (0-19 years) had been reported in a sample of 101 countries that collect age data.

The American Academy of Pediatrics reported that, as of July 15 this year, almost 4.09 million children in the USA have tested positive for Covid-19 since the start of the pandemic. In the week leading up to the report, 23,500 positive cases among children were counted.

These figures are likely to be underestimates. Estimating the true prevalence of Covid-19 infections among children is difficult due to limits of point-in-time serological testing, and because mild/asymptomatic cases in children lead to under-testing.

Children transmit less readily than adults, but they can and do transmit infection to household members, and the factors that contribute to this risk are still being worked out. Children do not appear to be the primary drivers of SARS-Cov-2 transmission in home or school settings, and - fortunately - often have mild illness or are asymptomatic.

Death from Covid-19 among children is thankfully rare compared with adults. A large systematic review by Kitano and colleagues found the case fatality rate in children, that is the proportion of children dying due to PCR-positive Covid-19 infection, ranged from one in 10,000 in high-income countries, to two in 1000 in low- and middle-income countries. Among children, infants under one year old sustained the highest case fatality rates from Covid-19, reaching one in 100 among Covid-19 positive infants in low- and middle-income countries.

However, we need to continue to be careful to not draw too firm conclusions yet about any future Covid-19 vaccination programmes for children based on these data. We cannot treat ‘children’ as a block category. Younger children have lower risk, older adolescents have incrementally higher risk.

We also need to fit our strategy to the unique population profile of children here in Aotearoa, and to our local healthcare capacity.

The American Academy of Pediatrics (AAP) reports that children make up a small proportion of those hospitalised from Covid-19, and that 0.1 percent to 1.9 percent of all child Covid-19 cases resulted in hospitalisation. That sounds reassuring, right? But wait, we first need to look at what this means over the whole population. That’s what epidemiology, the study of the distribution of disease over a population, is all about.

First, we need to consider the risks of severe disease - often defined as children needing to be admitted to hospital for supplemental oxygen and/or ventilation support - and whether it is worthwhile to reduce the burden of hospitalisation using immunisation.

In Aotearoa New Zealand, we routinely vaccinate to protect children from rotavirus, a nasty virus that causes gastroenteritis. Before its incorporation into the national immunisation schedule in 2014, rotavirus infected approximately one in five children, with 2 percent of infected children hospitalised - this is not dissimilar to the upper bound of the Covid-19 hospitalisation proportion reported by the AAP.

The introduction of the rotavirus vaccination led to an 85 percent reduction in hospitalisations for rotavirus for children under five in 2015, and this reduction has been sustained over time. This amounts to a reduction from 700 children under five being hospitalised with rotavirus every year, to now less than 100 hospitalisations every year. Vaccination has prevented a large number of hospitalisations.

Taking pressure off our hospitals and healthcare systems is key. We have a very low proportion of ICU beds per capita compared to other countries. The only dedicated paediatric intensive care unit in the country is at Starship Children’s Hospital, where doctors told the media in April this year that occupancy reaches critical levels every 48 hours. A fundraising campaign currently underway is asking the public to urgently donate money to fund more beds for the unit. Our hospitals and staff are stretched thin every winter. This vulnerability has been demonstrated during the current RSV epidemic. We have nursing shortages and approximately 50 percent of our medical specialists report high levels of burnout symptoms.

Accepting even a 1 percent hospitalisation rate for Covid-19 in children would mean needing to absorb large numbers of hospitalisations on top of existing health care shortages. We need to be very cautious about accepting preventable hospitalisations in children.

Secondly, the distribution of severe illness and hospitalisation will not be equitable. Children who are obese, or who have comorbidities (one or more existing medical conditions), are at higher risk of severe illness. A large meta-analysis of more than 285,000 children found severe Covid-19 (needing hospitalisation) present in one in 20 children with comorbidities including obesity, compared with two in 1000 children without comorbidities. US research shows that the risk of Multisystem Inflammatory Syndrome in Children (MIS-C) – a rare but serious complication of Covid-19 – is significantly higher in disadvantaged ethnic groups.

We have high proportions of children with obesity and comorbidities here compared with overseas: One in 10 of our children is obese. Consequently, it is very possible we would have higher proportions of children hospitalised compared to other developed countries if Covid-19 spread unchecked.

It is crucial to look at this from an equity point of view as Māori and Pacific children, and children from lower socioeconomic backgrounds, have higher levels of comorbidities and risk factors that predispose them to more severe illness. Allowing Covid-19 to spread unfettered would disproportionately affect these groups as well as the families who would take time off work to care for them.

We have already seen how Covid-19 has spread unevenly and unjustly overseas, with disproportionately higher spread and deaths among low socioeconomic communities and historically disadvantaged populations.

Thirdly, there is ongoing uncertainty regarding longer-term symptoms of Covid-19 infection in children, referred to as “long Covid”. UK government data shows 7.4 percent of children aged two-11 years and 8.2 percent of children aged 12-16 have ongoing symptoms 12 weeks after infection (data collected from parents’ self-report so we need to allow for uncertainty). But whatever the exact figures, the NHS has had to establish 15 long Covid medical clinics for children to manage clinical demand. We need more data to understand this phenomenon better, and studies are underway.

Early reports of cognitive difficulties following Covid-19 infection (‘brain fog’) are concerning in terms of potential impacts on the developing brain. As new variants continue to emerge, there is also ongoing uncertainty regarding how any new variants may affect children.

More than nine million US children aged 12-17 years have received at least one vaccine dose and trials in younger children are in the field, with results from Pfizer’s Phase 2/3 trial of children aged five-11 and two-five years expected later this year. We’d be smart to wait for these results. Formulating a strategy for children requires rigorous understanding of the efficacy and safety profile of potential vaccines. Perhaps it will look like advocating for children with risk factors to be vaccinated, as we do for influenza? Perhaps it will look like vaccinating all children who are a certain age upwards, as we do for other diseases? Other strategies include vaccinating children in key exam years as implemented in Israel, and prioritising children living in households where others are at risk. It’s not quite clear yet what the best future vaccination strategy will be for kids.

There is one thing we know for certain however. The safest and most equitable course of action at present is to not allow children to be exposed to Covid-19 in large numbers. Elimination continues to provide protection and clear benefits for children, families, and our health system, while we work it out.

Because of our successful elimination strategy, Aotearoa NZ has options. We have time to wait for more data. We can make an informed and equitable decision that will keep our healthcare system up and running. We shouldn’t rush to come to a judgment on vaccinating children.