COVID-19 vaccine weekly safety report – 01-07-2021

COVID-19 vaccine weekly safety report – 01-07-2021

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Since last week’s report, a further five reports of blood clots and low blood platelets have been assessed as confirmed or probable TTS likely to be linked to the AstraZeneca vaccine (Table 1). 

Table 1: Newly confirmed and probable TTS cases for the week of 25 June-1 July 2021‡

New confirmed TTS

New probable TTS

Two new cases:

Three new cases:

As previously reported, the TGA determines whether a report is likely to represent TTS by assessing cases against a consistent set of criteria, based on the case definitions established by the UK’s Medicines and Healthcare products Regulatory Agency.

 

This takes the total Australian reports assessed as TTS following the AstraZeneca vaccine to 41 confirmed cases and 28 probable cases, with a total of 69 cases overall from approximately 4.6 million doses of the AstraZeneca vaccine. 

When assessed against the criteria used by the US Centers for Disease Control and Prevention (CDC), fewer than half of the cases reported to TGA are classified as Tier 1 cases, which involve clots in an unusual location, such as the brain or abdomen (Table 2). Of note, Tier 1 cases tend to have more serious outcomes than Tier 2 cases. Tier 1 cases were less common in older people. Approximately one quarter of cases were classified as Tier 1 in patients aged 60 years or older, compared to approximately half the case in people aged less than 60 years.

Based on the information we have, about half of the Tier 1 cases had clots in the brain (cerebral venous sinus thrombosis – CVST) and half had clots in the abdomen (splanchnic vein thrombosis). Of those with clots in the brain, around half also had another clot in the leg (deep vein thrombosis – DVT) or the lungs (pulmonary embolism – PE). The Tier 2 and unclassified TTS cases had only the more common clots like deep vein thrombosis or pulmonary embolism.   

Table 2: Total confirmed and probable TTS cases to date by age and CDC classification

Age

Total cases

CDC classification†

Tier 1

Tier 2

Not classified

<30 years

1

1

30-39

1

1

40-49

4

4

50-59

20

9

6

5

60-69

13

3

4

6

70-79

19

6

5

8

80+

11

3

4

4

All ages

69

(34 men, 35 women)

26

20

23

† The US CDC classification is defined as:

  • Tier 1 = clots in an unusual location (such as the brain or abdomen) and a low platelet count with or without antibodies that activate platelets (anti-PF4 antibodies)

  • Tier 2 = clots found in common locations (such as the leg or lungs) and a low platelet count and anti-PF4 antibodies

  • Not classified = case does not meet the criteria for Tier 1 or Tier 2 (for example clots in common locations with low platelet count but no evidence of anti-PF4 antibodies).

Cases have most often occurred about two weeks after vaccination, although the time to onset (or diagnosis) has ranged from one to 44 days (Table 3). In some cases with a longer time to diagnosis, patients had experienced symptoms at an earlier stage but complicating factors, including symptoms from comorbidities, may have delayed a clear diagnosis. Approximately one in four TTS cases has required Intensive Care Unit (ICU) treatment, although all but three patients have since been released from ICU. 

Table 3: Time to onset, treatment and outcomes for TTS cases*

Time to onset/ diagnosis (days)

Median (range)

12 (1-44)

Treated in ICU

At any point†

18

Currently

3

Outcome

Discharged

51

In hospital

16

Fatal

2

*Data is based on the most recent medical information available to the TGA
†Last week’s report had an error in the ICU data. Three patients that were in ICU were not included in the total for patients that received ICU treatment at any point. This has been corrected above.

The TGA has sadly been advised by its UK counterpart, the Medicines and Healthcare products Regulatory Agency (MHRA), of the death of a woman in the UK five weeks after receiving her first dose of the AstraZeneca vaccine in Australia.   

While some of her symptoms, imaging results and pathology tests suggested TTS, the woman had another very serious and recent underlying health condition and UK authorities have ordered a post-mortem to assess whether this condition, along with the impact of long plane and car travel from Australia to the UK, had a role in her death.  

Her family has requested privacy, and we pass on our condolences to them at this sad time. 

It is not known whether she was an Australian citizen or permanent resident.

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