Rachel McDonald
Australian Science Media Centre
Safety data for the Pfizer vaccine in the 5–11 age cohort is beginning to roll in, with a paper published in NEJM this week reporting no serious side effects in a group of 1,500 children given two shots of the vaccine at a significantly lower dosage than adults currently receive. The researchers said the vaccine showed an efficacy of 90.7%.
Professor Sarah Palmer from the Westmead Institute of Medical Research told the Australian Science Media Centre (AusSMC) the study “further underscores the safety and efficacy of the Pfizer COVID-19 vaccine for children, which is one third the adult dose.
“We can see in the case of the United States there will soon be widespread vaccinations for children between the ages of five and 11. We should move promptly here in Australia to extend the same protections to children under the age of 12.”
While the vaccine appears safe in this study, Professor Robert Booy from the University of Sydney said the real-world results of COVID-19 vaccinations in adults showed testing a vaccine on a cohort of 1,500 was not enough to get the full picture on the rare side effects linked to mRNA vaccines.
“We need real-world information on 1,000 times as many children (1–2 million) to be properly reassured that young children do not experience rare but important serious side effects such as myocarditis and pericarditis,” Booy says.
“We know the incidence of myocarditis after mRNA vaccines is higher after the second dose than the first, higher in boys than in girls, and higher in teenagers than in young adults. There remains the real possibility that children aged five to 11 could have an even higher risk of myocarditis, despite the fact that only a 1/3 dose has been used in this study.”
While the risk of this condition in adults and teens is far outweighed by the potential complications of COVID-19, the fact children appear to be less susceptible to severe disease from the virus changes the balance of risk.
Australian and New Zealand Paediatric Infectious Diseases Group (ANZPID) co-chair Associate Professor Asha Bowen said Australia’s statistics on children aged five to 11 – more than 7,000 cases and 244 hospital admissions from January to October – do not paint the full picture of how unlikely severe illness is for them.
“Many cases in children are asymptomatic, some are likely to be undiagnosed, and a large proportion of hospital admissions are because of sick parents being unable to care for their children,” Bowen says. “Very few children have required specific antiviral or other treatments and a very small proportion (less than 1 in 3,000 cases) have required intensive care. There have been no deaths among five- to 11-year-old children, but sadly two adolescents have died with COVID in Australia,” Bowen said.
Fortunately for Australia, the rollout of vaccines for children in the US means the data on 1–2 million children that Booy says we need will soon be available.
In the meantime, an increasing number of Australian states will need to find a way to balance the risks of COVID-19 transmission in unvaccinated primary schools with the need to take students out of class as little as possible.
This challenge was the subject of one section of the Doherty Institute’s final modelling report presented to National Cabinet at the end of last week.
Dr Nick Scott from the Burnet Institute, who was involved in the modelling, told an AusSMC briefing this week the modelling centred on tracking how a single COVID-19 case would move through a school community over the next 45 days.
“Without any intervention, we saw that about 50% of the time,” Scott says. “It’s different for primary and secondary schools, we could expect to see either no further transmission or less than five infected in total.”
To manage the other 50% of the time when a case leads to an outbreak, Scott says the team looked at the impact of routine surveillance testing of students, which he says would significantly reduce the size of outbreaks if done twice a week.
The more outbreaks occur in a school community, he says, the more beneficial surveillance testing was.
They also tested isolating an entire classroom for a week when one student tests positive compared to a ‘test-to-stay’ approach. This means allowing exposed students to come to school anyway as long as they take a rapid antigen test each morning for the week they would otherwise be isolated.
“What we found was that the seven-day quarantine and the seven-day test-to-stay were approximately equivalent in terms of infection outcomes and outbreak risk, but the seven-day test-to-stay strategy had the considerable additional benefit that there were much less days of face-to-face teaching lost,” Scott said.
The government and relevant organisations will now consider whether they will bring this strategy into schools, and how soon. Should vaccines for five- to 11-year-olds be approved soon, Scott said the effectiveness of the strategy would only get better, reducing the risk of outbreaks occurring and reducing the size of outbreaks that do occur.
- You can access the full Expert Reaction on Pfizer vaccine safety here
- The full media briefing on the Doherty modelling can be found here
This article originally appeared in Science Deadline, a weekly newsletter from the AusSMC.
