Freja Kirsebom Profile picture
Senior epidemiologist - COVID-19 vaccines @UKHSA. PhD in the immunology of respiratory viral infections @imperial_college.
LittleGravitas 🇺🇦 🌻 🇪🇺 💙 #FBPE Profile picture Peter English #FBPE Profile picture lexx Profile picture Martin Profile picture 4 added to My Authors
Apr 28 14 tweets 3 min read
The first real-world data on the vaccine effectiveness (VE) of the AstraZeneca booster against symptomatic disease and hospitalisation with Delta and Omicron - new pre-print from us this week.…

1/14 The AZ booster is in use as part of numerous vaccine programmes globally, particularly in LMICs, due to the lower cost and the relative logistical ease of use. As such, there is a need to understand the duration & level of protection conferred in real world settings.

Mar 24 5 tweets 2 min read
Our most comprehensive analysis so far on the protection conferred by vaccines against hospitalisation over time is published today in the UKHSA Vaccine Surveillance report… Since Omicron causes milder disease and all individuals who are hospitalised for any reason in the UK are tested for COVID-19, an increasing proportion of cases in hospital are likely to have COVID-19 as an incidental finding rather than as the primary reason for admission.
Jan 27 7 tweets 2 min read
Two important updates from our team this week:

- Vaccine effectiveness (VE) against symptomatic disease after Omicron BA.2 shows that VE remains unchanged

- VE against death after Omicron BA.1 shows VE is 95% at 2+ weeks after booster


Full report… First, VE against BA.2.

The Omicron sub-lineage known as BA.2 was designated VUI-22JAN-01 on 19 January. VE against symptomatic disease was analysed in a test-negative case control design. Pillar 2 data from symptomatic cases tested between 27/12 & 21/01 were included.

Jan 14 8 tweets 3 min read
This week's updated analysis from our team on vaccine effectiveness against Omicron infection is now published in the UKHSA Technical Briefing.

Good news - protection from the boosters against severe disease continues to be well maintained.…

This week, individuals who reported symptoms and tested in Pillar 2 (community testing) between 27 November 2021 and 6 January 2022 were included in the analysis. This corresponded to 236,023 Delta cases and 760,647 Omicron cases.

Jan 7 14 tweets 4 min read
Today we publish our latest analysis where we stratify by age to investigate vaccine effectiveness (VE) against Omicron in adults aged 65 years and older in England.

1/14 This week's analysis is restricted to adults aged 65+ who reported symptoms and tested in Pillar 2 (community testing) between 27th November and 31st December 2021. Cases were defined as the Omicron or Delta variant based on whole genome sequencing, genotyping, or SGTF.

Dec 31, 2021 10 tweets 3 min read
This week, we were able to estimate vaccine effectiveness (VE) against hospitalisation for the first time. In short, good news. VE after a booster is close to 90%. The full update from our team is published in this week's technical briefing update:…

1/10 As before, we first used a test-negative case control study design to estimate VE against symptomatic disease. This analysis included tests between 27th November and 24th December, and included 169,888 Delta cases and 204,036 Omicron cases.

Dec 23, 2021 9 tweets 3 min read
An update from our team on the latest vaccine effectiveness (VE) estimates against symptomatic infection with the Omicron variant has now been published in the UKHSA Variant Technical Briefing 33 (page 24).…

With more data available, we now have better estimates of VE following a booster (Pfizer or Moderna) after either an AZ or Pfizer primary course. We still did not have enough data to estimate VE against hospitalisation but we will be looking at this as as soon as possible.

Dec 10, 2021 11 tweets 2 min read
Our first initial estimates of vaccine effectiveness (VE) against symptomatic disease with the Omicron variant are now out. In short, VE remains high following a Pfizer booster after AZ or Pfizer, but is reduced after two doses.

More below 👇

1/11 We used a test negative case control design to estimate VE against symptomatic COVID-19 with the Omicron variant compared to Delta. The odds of vaccination in PCR positive cases was compared to the odds of vaccination in those who test negative.