1/ Our preprint on #SARSCoV2 antibody responses in UK adults receiving a #COVID19 vaccine booster with the Pfizer vaccine at least 6 months after primary immunisation with Pfizer or AZ vaccine, which was given at an extended interval (8-12 wks) … 🧵

👉 medrxiv.org/content/10.110…
2/ We recruited adults aged 50+ years when they became eligible for their #COVID19 vaccine as part of the UK National Immunisation Programme. Participants provided regular blood tests for #SARS_CoV_2 antibodies at multiple intervals, including before & after the booster dose.
3/ 3 groups were assessed: (i) 2 Pfizer doses <30 days apart (Pfizer-control), (ii) 2 Pfizer doses ≥30 days apart (Pfizer-extended) or (iii) 2 AZ doses ≥30 days apart (AZ-extended) in London, England. Spike protein antibodies were compared before and 2-4 weeks after the booster Image
4/ We observed antibody waning after primary immunisation for all 3 groups. Antibodies peaked at 2-4 weeks after dose 2, before declining by 68% at 36-38 weeks after dose 2 for Pfizer-controls, 85% at 24-29 weeks for Pfizer-extended & 78% at 24-29 weeks for AZ-extended adults Image
5/ Before the booster, antibodies were highest in Pfizer-extended participants (942 [95%CI, 797-1113]) vs AZ-extended (183 [124-268]) participants at 24-29 weeks, or Pfizer-controls at 36-38 weeks (208; 95%CI, 150-289). Results for infection-naive adults below 👇 Image
6/ At 2-4 weeks after booster, antibodies were significantly higher vs primary vaccination in all 3 groups: 13,980 (11,902-16,421) in Pfizer-extended (15.9-fold) vs 10,799 (8,510-13,704) in AZ-extended (57.2-fold) & 18,104 (95%CI, 13,911-23,560) in Pfizer-control (76.3-fold) Image
7/ Pfizer-control participants (median:262 days) had longer interval between primary & booster doses than Pfizer-extended or AZ-extended (both median:186 days) ➡️ they started with lower pre-booster antibody levels & longer time for immune memory to mature than other the 2 groups
8/ Conclusion 1: boosting with Pfizer vaccine after 6 months provided very high antibody levels irrespective of primary immunisation with Pfizer or AZ

A longer interval between primary vaccination & booster provides higher post-booster responses ➡️ longer duration of protection?
9/ Conclusion 2: Boosters will not only provide additional protection for those at highest risk of severe COVID-19 but also prevent #SARSCoV2 infection and, therefore, interrupt transmission, thereby reducing infections rates in the population


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More from @ShamezLadhani

6 Oct
1/ Comparison of Symptoms and RNA Levels in Children and Adults With SARS-CoV-2 Infection in the Community Setting

👉 @JAMAPediatrics paper comparing kids vs adults - most findings are as expected but good to see them confirmed in a large study… 🧵

2/ This cross-sectional population-based survey included a convenience sample of 37,000 kids & adults in King County, Washington, who enrolled online for home self-collection of upper respiratory samples for SARS-CoV-2 testing from Mar-Nov 2020
3/ 37,067 samples were tested & 673 (1.8%) were #sarscov2 positive (1.6% in adults, 3.4% in kids)

Most kids (80%) had a known SARS-CoV-2 +ve contact, & most contacts (68%) were in the same household

But only 41% of SARS-CoV-2 +ve adults (41.4%) reported any known +ve contact
Read 9 tweets
17 Sep
1/ Household transmission of #SARSCoV2 in children & adults

This new @PHE_uk study was pre-Alpha, pre-Delta & pre-vaccine but provides important insight into household infection & transmission risks in kids & adults

Here’s what the study found … 🧵

👉 journalofinfection.com/article/S0163-…
2/ The study followed up 452 household members of 181 PCR-confirmed adult & child cases in England during Mar-Nov 2020.

Nasal swabs taken for #SARSCoV2 PCR at baseline & Day 7.

#SARSCoV2 Antibodies tested at baseline & Day 35 to detect symptomatic + asymptomatic infection Image
3/ 91/431 (21%) contacts were PCR +ve & 180/383 (47%) were antibody +ve at day 35 👉 194/431 (45%) contacts had PCR +/- antibody evidence of infection

After excluding 55 households with prior/co-primary cases & PCR -ve asymptomatic contacts, 75/248 *(33%)* contacts were infected
Read 8 tweets
14 Sep
1/ How long do 2 doses of #COVID19 vaccines protect for? Who needs booster vaccinations?

Our team @phe_uk have just published a pre-print on vaccine effectiveness (VE) and duration of protection after 2 doses of Pfizer and AZ vaccines in adults … 🧵

👉 khub.net/documents/1359…
2/ We now have data for ~6 months post-vaccination & compare VE by age, comorbidity & #sarscov2 strain (Alpha/Delta)

We used a test-negative case-control design to estimate VE after 2 doses against PCR-confirmed disease, hospitalisation within 14d of PCR test & death within 28d
3/ In this analysis, 2 million adults (38.7%) had 2x AZ, 1.7 million (31.7%) had 2x Pfizer, 124k (2.4%) had 2x Moderna & 10k (0.2%) had mixed/other

There were 1.5 million cases (544k Alpha, 895k Delta, 37k other/unknown) & 3.8 million negative tests from 3.3 million adults
Read 11 tweets
12 Sep
1/ Our paper on #SARSCoV2 infection, seroconversion and antibody positivity rates in English secondary schools following the emergence of the Alpha variant (B.1.1.7) is now online.

Here’s what we found …🧵

👉 journalofinfection.com/article/S0163-…
2/ We tested #SARSCoV2 infection and serum antibodies in nearly 2,000 staff and students attending 18 secondary schools in 6 English regions during Sep 2020, Dec 2020 and March 2021. Most students did not return to school after the Christmas holidays until their tests in Mar 2021 Image
3/ In March 2021, 1895 participants (1100 students:795 staff) were tested; 5.6% (61/1094) students and 4.4% (35/792) staff had laboratory-confirmed SARS-CoV-2 infection from December 2020-March 2021
Read 8 tweets
12 Aug
1/ Following a barrage of Twitter abuse because of my quote about our School Infection Survey (SIS) results today, I would like to reiterate what we have learnt about #COVID19 after 9 million students returned to full-time in-person education in England in March this year 👇
2/ The UK went into national lockdown including school closures in Jan 2021 following emergence of the Alpha variant. #COVID19 cases declined rapidly & schools reopened fully on 08 Mar 2021 (wk 10) when the rest of England remained in lockdown 👉 gov.uk/government/sta…
3/ During the 3 weeks until Easter holidays (wks 10-13, black circle), we saw a small ⬆️ in #covid19 cases among primary school kids (red line) & (because of mass rapid antigen testing before schools reopening) a large short-lived spike in secondary school kids (green) 👇
Read 11 tweets
9 Aug
1/ There have been increasing claims, mainly in North American news outlets, that the #SARSCoV2 DELTA variant is causing more severe #COVID19 in kids compared to previous variants

Well, everything we know so far indicates that’s it’s *not* true. Here’s why…🧵
2/ It’s true that the delta variant is more transmissible the both the alpha variant & the original strains, which means that it will infect more people more quickly, but there is no evidence that the risk of infection or transmission to others is different in kids vs adults
3/ Because of its higher transmissibility, there will be more Delta variant cases &, since most adults in many countries are vaccinated against #COVID19, cases/hospitalisations may seem disproportionately ⬆️ in kids (especially teens) vs adults. This just shows that #VaccinesWork
Read 13 tweets

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