Australia’s vaccine advisory body is unlikely to approve a second boost of the Covid vaccine for under-30s because of the increased risk of myocarditis and the diminishing benefit of successive doses.
Currently, Australians considered to be at higher risk of serious disease and those aged 30 and over can receive a fourth dose three months after their third dose.
With the country staring down a new wave of Omicron ahead of Christmas, some youngsters approaching a year since their booster shot are clamoring for another hit.
But Professor Allen Cheng, former co-chair and current member of the Australian Technical Advisory Group on Immunization (ATAGI), said The Sydney Morning Herald on Saturday that the current vaccine schedule was likely to remain as it is, given the increased risk of heart inflammation in young people.
“A 30-year-old who has Covid is probably not going to have problems with it unlike a 60- or 70-year-old,” Professor Cheng said. “It’s been a long time [an older person] we got his last dose, then we started to worry.
“A 30-year-old with … three doses will be optimally protected.”
He added: “Vaccines are beneficial and protective even for younger people, but the more doses you get, the less benefit you get from them and then we start to worry about causing side effects.”
ATAGI has been contacted for comment.
Given the rise in cases, state and federal health authorities have urged Australians to get another dose if they are eligible.
The Commonwealth’s chief medical officer, Paul Kelly, last week urged people to “make sure they are up to date with their vaccinations, including a third or fourth dose if you haven’t already had them”.
“Make an appointment for this dose as soon as possible so that your immunity is strengthened in the coming months when we are most likely to see an increase in the transmission of Covid-19 in Australia,” Professor Kelly said.
“Vaccination is your best protection against getting seriously ill or dying from Covid-19.”
Victorian health chief Brett Sutton also urged people to “keep up to date with any vaccine you are still eligible for”.
“A third dose, a fourth dose, whatever the dose is,” he said.
Professor Kelly said the latest wave was being driven by the Omicron XBB and BQ.1 variants, which he called “the Omicron grandchildren”.
According to the Department of Health, 96 percent of Australians over the age of 16 received two doses and 72 percent took three doses.
Among the eligible population over 30, only 42 percent – or just under 12 million people – received a fourth dose, while three-quarters of those over 65, or almost four million, did.
Talking to Nine’s Today Last week, Professor Kelly admitted that Australians had “high hybrid immunity to vaccination and previous infection”.
“So that will protect us against that more severe end of the disease spectrum, and that will continue even with these new variants, in my understanding,” he said.
“But we’re going to see more transmission, we’re going to see infections. And now is the time to really consider whether you’re up to date with that vaccine.”
“If you haven’t had your third dose and we’re all eligible for a third, if you haven’t had that fourth for those over 30 who are eligible for a fourth dose, now is the time to go and get that. That will protect you more .
“And now we have slightly modified vaccines with the B.1 strain as well as the original strain of the virus.”
Myocarditis and pericarditis are rare side effects associated with the Pfizer and Moderna mRNA vaccines, but studies suggest the risk is higher after Covid infection.
The Australian Department of Health says Covid is estimated to cause myocarditis at a rate of about 3.2 excess cases per 100,000, about the same risk as after vaccination.
But the risk after vaccination is much higher among boys aged 12 to 17, 13 cases per 100,000 for Pfizer and 24 per 100,000 for Moderna, according to the Therapeutic Goods Administration (TGA).
For men under 30, the rate is nine per 100,000 for Pfizer and 23 per 100,000 for Moderna.
“In men aged 16 to 40, it is uncertain whether the risk after Covid-19 remains greater than the risk after vaccination,” the Department of Health says in its current guidance.
ATAGI said last month that even despite this uncertainty, the threat of the virus continues to outweigh any risk that mRNA vaccines contribute to in the younger population.
“Booster doses of the Covid-19 vaccine are important to maintain protection and are recommended for men aged 16 to 40,” a spokesperson said in a statement.
As of October 30, 2022, the TGA says it has received 704 reports of probable myocarditis from about 44.2 million doses from Pfizer and 115 from about 5.4 million doses from Moderna.
Of 14 confirmed deaths related to Covid vaccines in Australia, only one was associated with myocarditis.
The TGA’s external Vaccine Safety Investigation Group (VSIG) concluded in September that the death of a young woman in her 20s, just weeks after receiving a booster dose of Moderna, was likely due to the vaccine.
“After careful consideration, the panel agreed that this woman’s myocarditis was probably related to vaccination, but recognized that there were other complicating factors that may have contributed to her death,” the TGA said at the time.
“Based on the current evidence, the panel reaffirmed that, overall, the benefits of vaccination at the population level continue to far outweigh the risks of mRNA vaccines.”
“No infection link”
Australia’s Department of Health cites two studies, one cohort study from four Nordic countries and one from the UK, for its claim that Covid infection causes myocarditis.
Contradicting those findings, Israeli scientists investigating the link between heart inflammation and Covid said they found “no increase” in myocarditis and pericarditis up to six months after infection.
The large population study of nearly 790,000 Israelis, published in the Journal of Clinical Medicine Earlier this year, it sought to determine the incidence of post-Covid heart disease in unvaccinated patients.
The researchers, from the Hebrew University of Jerusalem and Tel Aviv University, analyzed the medical records of Clalit Health Services, Israel’s largest mandatory health insurer that covers more than 50 percent of the population, or about 4.4 million people, from March 2020 to January 2021.
The dates were chosen to largely fall before the rollout of large-scale vaccination, which began in late December 2020.
A group of nearly 214,000 adults who had a documented positive PCR test in that time period were compared with a control group of about 936,000 patients with at least one recorded negative PCR test and no positive prior infection.
Diagnosis codes for myocarditis and pericarditis were extracted between 10 days after infection and up to six months after recovery.
Each patient in the Covid group was “matched” with three patients in the control group of the same age and sex.
During the study period, nine cases of myocarditis and 11 cases of pericarditis were detected in the Covid cohort, while in the control cohort 27 cases of myocarditis and 52 cases of pericarditis were detected.
“No statistical difference was observed in the incidence rate of both myocarditis (p=1) and pericarditis (p=0.17) between the Covid-19 cohort and the control cohort,” the authors wrote.
“In the current large population study of subjects, who were not vaccinated against SARS-CoV-2, we did not observe any increase in the incidence of myocarditis or pericarditis from day 10 after SARS-CoV-2 positivity.”
They added: “Multivariate analysis showed that male gender is associated with a higher risk of developing myocarditis or pericarditis, regardless of previous Covid-19 infection.”
The authors said the study had its limitations, such as the small number of cases relative to the sample size.
“Second, we included only inpatient cases with myocarditis or pericarditis, while outpatient medical records were excluded from the study,” they wrote.
“This could miss a small number of patients with mild disease.”
They noted that more long-term studies would be needed.
The Department of Health has been contacted for comment.
Originally published as the fourth dose of the vaccine, it is unlikely to be approved for children under 30 years of age due to the risk of myocarditis