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Dr Zoë Hyde Profile picture
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26 Jun, 5 tweets, 3 min read
I’m not confident the Sydney delta variant outbreak will be contained. This fundamentally changes the risk/benefit ratio of the AstraZeneca vaccine for those over 60.

Even a single dose provides >70% protection against hospitalisation & is worth the 0.00002% risk of blood clots.
A person aged over 60 years has at least a 7% chance of being hospitalised if they become infected with the original strain of the virus.

This rises to at least 10% with the alpha variant (B.1.1.7).

The risk likely exceeds 20% with the delta variant.
bmj.com/content/373/bm…
The risk of death from COVID-19 also rises steeply with age.

The figure below shows the estimated proportion of people who die after becoming infected with the original strain of the virus.

Remember the delta variant is associated with additional risk.
link.springer.com/article/10.100…
While use of the AstraZeneca vaccine will not be sufficient to achieve herd immunity, it will keep people out of hospital.

This must be the immediate aim now that the delta variant is circulating in Sydney.
Here’s preliminary data from the UK showing the estimated effectiveness of the AstraZeneca & Pfizer vaccines against hospitalisation for COVID-19:
khub.net/documents/1359…

And here’s the estimated risk of blood clotting caused by the AstraZeneca vaccine:
health.gov.au/news/atagi-sta…

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More from @DrZoeHyde

Dr Zoë Hyde Profile picture
16 Jun
(1/4) Study showing the B.1.1.7 (alpha/UK) variant is associated with a 52% increase in the risk of being hospitalised compared to the original strain. The increased risk mainly affects those aged 30 years and older. The risk of death is increased by 59%.
bmj.com/content/373/bm…
(2/4) The authors also calculated the absolute risk of being hospitalised after testing positive with the B.1.1.7 (alpha/UK) variant.

For children (<10 years old), it was about 1%, and for adolescents, it was 0.7%.

This was not significantly different than the original strain.
(3/4) For 20-29 year olds, the absolute risk of being hospitalised was 1.9% (previously 1.5%).

For 30-39 year olds, the absolute risk of being hospitalised was 3.4% (previously 2.6%).
Read 4 tweets
Dr Zoë Hyde Profile picture
13 Jun
UK pre-print study showing people infected with the delta variant (B.1.617.2, first identified in India) were 64% more likely to transmit the virus to household members than those infected with alpha (B.1.1.7/UK).

⚠️ Children were 46% more likely to transmit than young adults.
While most older adults have been vaccinated (making them less likely to transmit if infected), less than half of younger adults have been vaccinated.

The higher risk of transmission by children is therefore unlikely to be entirely explained by the vaccination of adults.
It is also likely that many (if not most) of the adult index cases in this study were either unvaccinated, or only partially vaccinated.

Additionally, data published by the UK government last year showed children were more likely to transmit than adults.
gov.uk/government/pub…
Read 4 tweets
Dr Zoë Hyde Profile picture
11 Jun
New data suggest the Pfizer-BNT & Moderna mRNA vaccines are associated with an increased risk (16 cases per million doses) of developing heart inflammation in adolescents & young adults. However, the majority of cases were mild (>80% fully recovered).🧵
fda.gov/media/150054/d…
What does this mean?

For young adults, the benefits of vaccination still outweigh the risks.

For children, the picture *with mRNA vaccines* is less clear and requires careful evaluation of the benefits and potential risks.
Although children are unlikely to develop severe COVID-19, they are at risk of long COVID, and can rarely develop a severe multi-system inflammatory syndrome.

They are also able to transmit the virus to others, including their family members. This may also harm children.
Read 7 tweets
Dr Zoë Hyde Profile picture
5 Jun
The latest data from the UK’s Office for National Statistics show that over 1 million people in Great Britain are estimated to be living with long COVID.

Nearly 400 thousand of these have been living with long COVID for at least one year.

A thread. 🧵
ons.gov.uk/peoplepopulati…
The most common symptoms reported by people living with long COVID were fatigue, shortness of breath, muscle pain, and difficulty concentrating.

However, it is possible that some of these symptoms could be attributable to a cause other than long COVID in at least some people.
Of the people living with long COVID, nearly two-thirds (63.7%) reported some limitation in their daily activities.

Nearly one in five (18.8%) reported that they were limited a lot. That means at least 192,000 people in the UK now experience disability as a result of long COVID.
Read 7 tweets
Dr Zoë Hyde Profile picture
4 Jun
New data from England confirm the B.1.617.2 (delta) variant (which originated in India), is more concerning than B.1.1.7 (alpha/UK).

Household secondary attack rate is increased 1.5 times. Hospitalisation is increased 2.6 times. Schools are playing a major role in its spread. 🧵
Remember the B.1.1.7 (alpha/UK) variant is more transmissible than the original strain, and more likely to lead to hospitalisation.

The increase in attack rate and risk of hospitalisation seen with B.1.617.2 is *on top of* the increase seen with B.1.1.7.
There are now clear signs of a growing B.1.617.2 epidemic in the UK.

While cases caused by the B.1.1.7 (alpha/UK) variant are decreasing, B.1.617.2 cases are growing. The majority of S-gene positive cases depicted in green in the graph below are likely to be B.1.617.2 cases.
Read 6 tweets
Dr Zoë Hyde Profile picture
2 Jun
Representative antibody study of Iquitos, Peru, after their devastating 1st wave. Over two-thirds of the sample had SARS-CoV-2 antibodies, suggesting 70% of the city had been infected. Children were more likely to have antibodies than adults (except >=60).
thelancet.com/journals/langl…
Although 70% of the city’s population had previously been infected, this was insufficient to prevent a second wave beginning in January 2021 caused by the P.1 variant. This suggests herd immunity can’t be reached by natural infection, which is less effective than vaccination.
Interestingly, a very high proportion of children had been infected, despite school closures. However, Iquitos is a very poor city and most residents have to leave home to purchase food on a daily basis. Children are likely more exposed to the community than in other settings.
Read 5 tweets

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