Thread by @jeffgilchrist

COVID-19: UK vaccine updates: Boosters for 50+

JCVI is now recommending booster shots (3rd dose) be offered to those more at risk of serious disease for the following groups no earlier than 6 months after getting the second dose ( gov.uk/government/new… ). 🧵1/

- those living in residential care homes for older adults
- all adults aged 50 years or over
- frontline health and social care workers
- all those aged 16 to 49 years with underlying health conditions that put them at higher risk of severe COVID-19, and adult carers

2/

- adult household contacts of immunosuppressed individuals

3/

Many higher risk people already received their second shot 6 months ago and JCVI are not sure if sufficient levels of protection will remain from 6 to 12 months so using the precautionary principle are recommending 6 months as a booster time frame to be on the safe side. 4/

Therefore they recommend the booster program start as soon as operationally possible. JCVI also advises a preference for people to get the Pfizer vaccine for the booster regardless of which brand they had for their initial shots. 5/

This is from data in the COV-BOOST trial that indicates the Pfizer vaccine is well tolerated as a third dose and provides a strong booster response. 6/

Alternatively a half-dose of the Moderna vaccine may be offered (a standard Moderna dose is 100 ug vs 30 ug for Pfizer) likely to reduce the number of reactions. 7/

Public Health England released data justifying the 3rd shot boosters in the UK ( assets.publishing.service.gov.uk/government/upl… ). 8/

You can see that effectiveness against hospitalization for those 65+ who are not in a clinical risk group remains at 95% for Pfizer but dropping more significantly in those who received the AZ vaccine (

https://twitter.com/EricTopol/status/1437890711139995648

). 9/

The effectiveness drops more rapidly for those 65+ in a clinically extremely vulnerable group so it would make sense to target that specific group for 3rd doses. 10/

PHE compared symptomatic infection rates for those 80+ who received their doses less than 4 weeks apart which is the standard Pfizer dose interval that was used in Israel and the USA, and 8+ weeks which was more common in the UK and Canada (

https://twitter.com/jburnmurdoch/status/1438100723753967617?s=20

). 11/

Lab studies previously showed a stronger immune response with 8+ week dose intervals compared to <4 weeks, and this real world data seems to confirm. A 3 week gap between doses appears to produce weaker levels of protection. 12/

This could also help explain why Israel is seeing faster waning of their vaccine against symptomatic infection than other parts of the world that implemented longer dose intervals. 13/

Looking at protection against hospitalization, apart from the very elderly, Pfizer shows very little waning while AZ shows slight waning but still close to 80% efficacy after 5 months (

https://twitter.com/jburnmurdoch/status/1438100728623546373?s=20

). 14/

Researchers found very little waning for Pfizer even among the elderly when looking at protection from death. Only modest waning for AZ but still 80% protection after 5-months being fully vaccinated (

https://twitter.com/jburnmurdoch/status/1438100740946501634?s=20

). 15/

From the data itself it looks like not everyone *needs* a booster. Most people < 65 and even for some healthy people 65+, protection is still holding up very well except for those with serious underlying health conditions where boosters could make a big difference. 16/