THE prospect of vaccinating children and teenagers for COVID-19 has had experts divided due to the lack of clinical trial data to date. But now that the Delta variant is affecting more and more younger people, not vaccinating them could potentially leave them vulnerable to new mutations of the virus, a viral immunologist from the Hunter says.
Following the TGA's approval of the Pfizer vaccine for children aged 12 and up last week, Associate Professor Nathan Bartlett said while the concept was emotive, ultimately, ongoing transmission and the re-opening of international borders could lead to new strains of the virus being introduced. Should the majority of the adult population be vaccinated, the virus would seek out the most susceptible groups - those without protection, Professor Bartlett, of the University of Newcastle, said.
"We don't know what other version of this virus is around the corner and could be brought in," he said. "While ever younger people are a reservoir of infection and there is transmission occurring, this virus has the capacity to mutate.
"That is certainly one concern with leaving a substantial number of people in that age group unvaccinated."
Associate Professor Bartlett said although Pfizer has now begun clinical vaccine trials in children aged six months to 11 years - in addition to trials for those aged 12-to-16 - earlier versions of the virus did not seem to cause infection or "overt disease" in younger people, so the focus was on adults.
"That has all changed now with the Delta variant," he said. "It is affecting younger people and causing disease in much younger age groups."
Associate Professor Bartlett said leaving children unvaccinated would also likely lead to a rise in "breakthrough" infections, even in people who are fully vaccinated. The virus had been infecting adolescents in schools in the UK and the US, who were bringing it home.
"Most of them aren't becoming seriously ill, but they are symptomatic," he said. "If a fleeting exposure to Delta is enough to become ill with COVID, when you are at home with a child who is infected, the protection your vaccine is affording is under a massively increased challenge 24 hours a day - and that looks to be causing breakthrough infections and symptomatic disease."
Associate Professor Bartlett said the UK had not opted to vaccinate teenagers except those at "high risk", but the US and Canada had, as have other countries in Europe.
"Children are a source of transmission," he said. "The virus will continue to replicate and transit in that age group and it is another source of potential variants.
"We can't predict what that will do for the evolution of the virus. They will also be a source of infection that will infect others who are else not protected or susceptible.
"I think they should be brought into the strategy, even if they are at the back of the queue. The sooner we can get everyone at risk vaccinated the better."