The TGA is “closely monitoring” adverse events related to COVID-19 vaccines, finding a rate of three cases of rare clotting syndrome per million doses
There have been 10,619 adverse events reported across 1,586,252 doses of COVID-19 vaccines administered in Australia, according to the TGA’s latest report up to 18 April.
This equates to a reporting rate of 6.7 adverse events per 1000 doses.
The AstraZeneca COVID-19 vaccine’s most frequently reported adverse events to 11 April were expected vaccine side effects such as headache, fever, muscle pain, chills and fatigue.
Adverse events of special interest reported for the AstraZeneca COVID-19 vaccine include anaphylaxis (48 reports), bleeding disorder (47 reports), seizure (19 reports), loss of sense of taste or smell (10 reports), low platelets (five reports), facial weakness (four reports), liver injury (three reports).
Assessment of reports against the accepted case definition for anaphylaxis indicates a rate of less than 10 reports per million doses of the AstraZeneca COVID-19 vaccine.
The overall number of reports of blood clots in the veins or arteries for the AstraZeneca vaccine is no higher than the expected background rate for the more common type of blood clots in Australia.
These can occur in around 50 Australians every day, separate to vaccination.
While there has been an increase in cases of blood clots submitted to the TGA, this appears to be due to reporting of coincidental blood clots unrelated to vaccination, “due to increased awareness of investigations into a rare and unusual clotting syndrome involving thrombosis (blood clots) with thrombocytopenia (low blood platelet count) following the AstraZeneca COVID-19 vaccine,” said the TGA.
“We are carefully reviewing any Australian reports of possible blood clots following vaccination with the AstraZeneca COVID-19 vaccine to identify any further possible cases of this disorder to better characterise this potential risk, which is now referred to as ‘thrombosis with thrombocytopenia syndrome’ (TTS),” it said.
The total number of TTS cases reviewed by the independent expert Vaccine Safety Investigation Group and likely to be linked to vaccination is three, as of 16 April 2021.
Based on this, the reported rate of TTS in Australia is approximately three per million doses (from 926,424 doses to 16 April 2021).
The reported rate in the UK, where more than 20 million doses of the vaccine have been given, is approximately five reports per million doses.
Healthcare professionals have been asked to be alert to the signs and symptoms of thromboembolism and thrombocytopenia as well as coagulopathies.
“Vaccinated individuals should be instructed to seek immediate medical attention if they develop symptoms such as a severe or persistent headache, blurred vision, shortness of breath, chest pain, leg swelling, persistent abdominal pain or unusual skin bruising and/or petechia a few days after vaccination,” said the TGA.
Meanwhile there have been five reports of low platelets up to 11 April 2021.
Two of these have been associated with thrombosis and confirmed as TTS cases as previously discussed.
The number of reports of low platelets overall is no higher than the expected background rate in Australia.
Up to 11 April, the most frequently reported adverse events for the Pfizer vaccine were headache, muscle pain, nausea, fever and fatigue.
These were side effects commonly reported in clinical trials.
Meanwhile adverse events of special interest reported for the Pfizer vaccine include 45 reports of anaphylaxis, 15 reports of bleeding disorder, 10 reports of facial weakness, 10 reports of seizure, seven reports of loss of sense of taste or smell, and three reports of a cardiac event.
There have been no reports of deaths associated with suspected anaphylaxis, and experts have determined that while many cases reported as anaphylaxis may appear similar to an anaphylactic reaction, they do not meet the accepted case definition.
The TGA estimates a rate of 35 cases of anaphylaxis per million doses of the Pfizer vaccine, although it is undertaking further assessment and states this rate may be an “overestimate”.
It reminds healthcare practitioners: “Routine vaccination procedures include keeping people under observation for 15 minutes after vaccination and having appropriate medical treatment on hand so that anaphylaxis can be rapidly managed, if it occurs.
“A second dose of [the Pfizer vaccine] should not be given to those who have experienced anaphylaxis to the first dose.”
The overall number of reports received of bleeding and blood clot disorders, such as stroke, pulmonary embolism and deep vein thrombosis for the Pfizer vaccine is no higher than the expected background rate for the more common type of blood clots in Australia.
Reported events are not related to the very rare clotting disorder associated with very low platelets being investigated in relation to the AstraZeneca COVID-19 vaccine, said the TGA.