Vaccine myocarditis risk reaches 1 in 10,000 for adolescent boys
- Category: Covid Vaccine Induced Myocarditis
- Created: Tuesday, 07 December 2021 11:49
- Written by Matt Woodley - RACGP
But while the rate of Pfizer-related myocarditis continues to increase in males aged 12–17, research cited by the TGA indicates the risk is still dwarfed by the threat COVID-19 poses to this cohort.
The latest Therapeutic Goods Administration (TGA) COVID-19 vaccine weekly safety report shows myocarditis is occurring at a rate of 10.6 cases per 100,000 second doses in males aged 12–17.
The new figures are an increase on those produced two weeks prior, in which the rate was only 8.5 cases per 100,000 second doses, while the overall second dose risk has also grown slightly.
However, research cited by the TGA suggests the risk–benefit profile still supports vaccinating this group. While yet to be peer-reviewed, it indicates that myocarditis occurs at a rate of 87.6 cases per 100,000 COVID-positive males aged 12–17 (Wilson score interval 402–1911 cases per 100,000).
Rates of myocarditis cases following Pfizer
|Age (years)||All doses||Second doses|
|Rate per 100,000 doses||Rate per 100,000 doses|
The TGA also updated the total number of reported cases of suspected myocarditis in Australia following vaccination to 730 – an increase of 138 over the past two weeks.
Meanwhile, 46 cases were deemed ‘likely myocarditis’ in the past fortnight, taking the overall total to 375 – 114 of whom were teenagers aged 12–17.
Moderna vs Pfizer
According to the TGA, the current overall estimated rates for the entire population of myocarditis for Pfizer and Moderna are similar – 1.4 cases per 100,000 Pfizer doses versus 1.8 cases per 100,000 Moderna doses.
However, statistical analysis shows that there is more uncertainty around the reporting rate for Moderna (likely to be between 1.2 and 2.5 cases per 100,000 doses) than for Pfizer (likely to be between 1.3 and 1.6 cases per 100,000 doses).
‘Because the number of cases of myocarditis reported after Moderna in Australia is small, we are not yet able to calculate reliable reporting rates for it or to see any difference in risk between the two vaccines,’ the TGA stated.
‘In some countries, higher rates of myocarditis and pericarditis have been reported with Moderna than with Pfizer.’
Thrombosis with thrombocytopaenia syndrome
Australia has recorded 166 cases of thrombosis with thrombocytopaenia syndrome (TTS) from about 13.5 million administered AstraZeneca doses. Of these, 144 (82 confirmed, 62 probable) related to a first dose, and 22 cases following a second dose (6 confirmed, 16 probable).
These figures include two new cases of TTS reported this week, an 80-year-old man from Victoria (following a first dose) and a 62-year-old man from NSW (following a second dose).
TTS occurs in Australia at a rate of about 2 out of every 100,000 people after a first dose, and 0.3 out of every 100,000 people after a second dose. The overall chance of death is less than one in a million.
Time to onset, treatment and outcomes for TTS cases
|First dose||Second dose|
|Median time to onset/diagnosis||Median (range)||13 days (1–94)||11 days (2–69)|
|Treated in ICU||At any point||47||1|
The TGA has received 156 reports of suspected Guillain-Barre Syndrome (GBS) occurring after vaccination with AstraZeneca. However, some suspected cases may not be related to vaccination, as GBS can occur after common viral infections and some types of gastroenteritis.
GBS has been reported in about one in every 100,000 people following vaccination with AstraZeneca.
From the beginning of the vaccine rollout up until 28 November, more than 39.1 million doses of COVID-19 vaccines have been given in Australia, including 24.4 million doses of Pfizer, 13.5 million doses of AstraZeneca, and 1.2 million Moderna doses.
A total of nine people are confirmed to have died as a direct result of vaccination against COVID-19 (0.00002%).
- AstraZeneca COVID-19 Guillain-Barre Syndrome Moderna mRNA myocarditis Pfizer TGA TTS
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