How does Covid-19 infection affect children? And what can we do to keep them safe? Paediatrician Jin Russell addresses the questions on the mind of many.

In the current delta outbreak in Aotearoa, children and young people under the age of 20 currently comprise approximately one third of the total number of cases.  Children under the age of 12 will remain the last susceptible group to Covid-19 infection in the population because a vaccine is not yet available for them. How concerned should we be about this?

As older age groups are increasingly vaccinated, we should expect that an increasing proportion of positive cases will be found among children

We should expect more cases in children for two reasons. Firstly, the absolute number of children who will be infected with Covid-19 will rise as the delta outbreak in Aotearoa grows. Secondly, children under the age of 12 will comprise an increasing proportion of positive cases in the outbreak because older age groups are being increasingly vaccinated and protected, leaving children as the largest susceptible group left in the population.

We can see that this shift has already begun by reviewing data from the Ministry of Health. If we look at all Covid-19 cases in Aotearoa since the start of the pandemic, children and young people under the age of 20 comprise 23.7% of all cases. However, this proportion has increased to 34% in the current August delta outbreak. This same pattern of children comprising an increasing proportion of positive cases as the pandemic progresses has also been observed in Australia.

Children are most likely to be infected by an adult in their household bubble than from other sources, including other children. Ensuring that as many eligible people as possible are fully vaccinated is crucial to preventing children from being infected. Being fully vaccinated reduces the likelihood of transmitting the virus onwards. Even for delta, fully vaccinated people with breakthrough infections are infectious for shorter periods of time than infected unvaccinated people. 

How does Covid-19 infection affect children? 

I have recently come across a lot of understandably very anxious parents online who are worried how Covid-19 infection may affect children. I recently wrote on how Covid-19 infection affects children here and have previously cautioned that we should take paediatric Covid-19 infection seriously here. However, being as reassuring as possible is important, because without good information, some parents may feel so anxious that they may not want their children to return to school at all, and this is not a good outcome either. Children pick up on the emotions of their carers, including emotions like stress and anxiety. So let’s take a look at this in more detail.

Because Australia has had larger outbreaks and recorded over 41,000 cases in children and young people under the age of 20, we can learn from Australian paediatric Covid-19 data and lean on the experience of Australian paediatricians.

Paediatricians and paediatric epidemiologists at the Murdoch Children’s Research Institute in Melbourne – a world-leading paediatric research institute – have recently published an excellent research evidence brief on Covid-19 and child and adolescent health. The majority of children who are infected with Covid-19 experience a mild or asymptomatic infection, similar to other common viral illnesses in children. Typical symptoms are fever, cough, a sore throat, blocked or runny nose, muscle aches and fatigue. Less commonly, diarrhoea and vomiting, and changes in smell or taste can occur. The Murdoch researchers also noted that it is common for children to experience multiple respiratory viral infections in childhood, such as influenza and respiratory syncytial virus (RSV). RSV is a leading cause of hospitalisation among New Zealand children, with an estimated six in every 1,000 children in the population under the age of five needing hospitalisation every RSV season. There is currently no vaccine for RSV.

The Australian and UK experience suggests that 1% to 2% of infected children are admitted to hospital due to Covid-19 but admissions are often mild or precautionary or brief such as a brief stay for rehydration, or oxygen, before being discharged home again.

There is no clear evidence that the delta variant causes more severe illness in children than other variants. Severe Covid-19 illness – typically pneumonia needing hospitalisation or ICU care – is rare among children. In the New South Wales winter delta outbreak, only 5 (0.2%) of 2864 paediatric Covid-19 cases needed intensive care, and these were all young people aged 15-18 years old who were, sadly, unvaccinated. Multisystem Inflammatory Syndrome in Children (MIS-C) is a rare but serious complication which can occur up to one month after infection. To mid-September 2021, there had been four cases of MIS-C in Australia with no deaths, and paediatricians are reportedly getting better at treating it. 

Even though Covid-19 is generally mild for children, I still believe we need to take special care to protect children and young people from being infected. Here are four reasons why …

1. If delta surges in our community, even infrequent outcomes such as hospitalisation, and rare outcomes, can become more commonplace. Remember the RSV outbreak earlier this year that stretched our paediatric services to the limit? More than 900 children were admitted to Wellington hospitals alone over June and July this year due to respiratory illness during the RSV outbreak. In a similar way, if delta was to surge, an increase in paediatric hospitalisations could be expected as has been seen in some US states.

2. Paediatric hospitalisations and severe illness will be inequitable. Children with pre-existing conditions are at a higher risk of needing hospitalisation due to Covid-19. In a systematic review of over 285,000 children, hospitalisation due to Covid-19 occurred in one in 20 children with pre-existing conditions, and in only two in 1,000 of children without pre-existing conditions. This pattern is seen with other respiratory viruses and is one of the reasons why children with certain pre-existing conditions are recommended to be vaccinated against influenza every year. Children from socioeconomically disadvantaged families and children of ethnic minority status are also at increased risk of severe illness. Even though paediatric hospitalisations tend to be minor and brief, these can all add up across the whole population to create a pattern that’s unacceptably inequitable, particularly for Māori and Pacific children.

3. Even though infected children may be less likely to transmit the virus compared to adults, they still can and do transmit to their household bubbles. My concern is for household members who are either unvaccinated, or who are vulnerable despite being fully vaccinated. It is so important that anyone who is eligible gets vaccinated as soon as possible.

4. Finally, there is still quite a lot we don’t know about Covid-19. Some children have persisting symptoms, often referred to as Long Covid. In general this phenomenon appears to be less frequent and less severe than in adults but more research is needed, especially as it would be helpful to factor in the possibility of persisting symptoms into vaccination decisions for children. The MCRI research brief cautions that much of the research completed so far is of poor quality. In the meantime, it is wise to seek to protect children from being exposed to the virus in large numbers.

Reopening secondary schools may increase community transmission but we can take steps to prevent spread within schools

I have previously written about what a gold standard plan for preventing Covid-19 transmission within schools looks like. Improving ventilation, air filtration (cleaning the air), using well-fitted masks, physical distancing, and hygiene, are all known to reduce Covid-19 transmission within schools, particularly when these preventative measures are layered up.

Modellers from Te Pūnaha Matatini have cautioned that the decision to reopen secondary schools in Auckland this week for NCEA students risks an increase in community transmission. Even though preventative measures within the school can curb the risk of transmission, spread could also increase because of after school gatherings, activities and conversations at the school gate. To keep transmission low, it’s vital that everyone continues to follow the rules for gathering outdoors only, and only two households at a time.

The vaccine mandates for educators will soon lift vaccination levels among school staff to close to 100% and this will significantly prevent Covid-19 spread within schools. Getting on with vaccinating eligible adolescents will also help tremendously. The good news is that adolescents are rapidly becoming vaccinated. Almost 78% of 12- to 19-year-olds in Aotearoa have received their first dose, and almost half have been fully vaccinated. This is a terrific achievement given the short timeframe in which vaccination has been available to young people. It would be smart to couple reopening schools with vaccination clinics available on site or nearby in suburbs with low vaccination coverage, removing all barriers for young people who want to be fully vaccinated. It is expected that the FDA will decide on whether to approve the Pfizer vaccination for 5- to 11-year-olds in the US very soon.

Doing our best 

Doing our best for children and young people in the pandemic means protecting them not just from direct impacts of the virus – such as infection, but also from the indirect impacts of the pandemic – prolonged school closures, isolation and sick loved ones. As the rest of us become vaccinated and protected, let’s not leave children behind in our planning.

Dr Jin Russell is a developmental paediatrician in Auckland, and a PhD student in life-course epidemiology at the University of Auckland. She is a former member of the NZ Policy and Advocacy Committee and College Council of The Royal Australasian College of Physicians.