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Shamez Ladhani Profile picture
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29 Jul, 6 tweets, 4 min read
1/ It was the JCVI that used basic immunological principles of vaccination to recommend a 12-week interval between #COVID19 vaccines to save more lives during the Alpha wave in the UK

Our paper (preprint) here shows why that was the right decision…🧵

👉medrxiv.org/content/10.110…
2/ We tested #SARSCoV2 antibodies in adults aged 50-89 years and found that, for both Pfizer & AZ vaccines, 95% had seroconverted (developed antibodies) by 35-55 days after the first #COVID19 dose, and 100% by 7+ days after the second dose

👉 medrxiv.org/content/10.110…
3/ BUT, when the vaccines were given 9-11 weeks apart, antibody levels at 2-5 weeks after 2nd dose were 6x ⬆️ for Pfizer (6703; 95%CI, 5887-7633) than AZ (1093; 806-1483), which in turn were higher than Pfizer given 3-4 weeks apart (694; 540 - 893) 👉medrxiv.org/content/10.110…
4/ Across England, for both #COVID19 vaccines, effectiveness (VE) was ⬆️ in all age-gps from 14 days after dose 2 vs dose 1, but varied with dose interval, with higher 2-dose VE when Pfizer doses were given >6 weeks apart compared to a 3-week schedule, including ≥80 year-olds
5/ When assessing vaccine effectiveness (VE) by interval between the two #COVID19 vaccine doses, the “sweet spot” does seem to be around the 8 week interval for the two vaccines, which supports the recent national recommendations to reduce the dose interval from 12 to 8 weeks
6/ In summary,

- The violin plot👇 shows nicely how extending interval between #COVID19 vaccine doses improves immune response after 2nd dose

- Remember that extending dose interval to 12 weeks meant many more older adults could be vaccinated quicker with limited vaccine supply

• • •

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More from @ShamezLadhani

Shamez Ladhani Profile picture
27 Jul
1/ On 19 July 2021, JCVI published their statement on #Covid19 vaccination for 12-17 yr-olds

If you only heard that JVCI did not recommend vaccine for teens then you missed out on a wealth of information & recommendations in the report

Here’s why 🧵

👉 gov.uk/government/pub…
2/ First, the MHRA & JCVI have very different functions. The MHRA authorises medicines, including vaccines, & monitors their safety but does not make vaccine recommendations. The JCVI makes recommendations on vaccines for the national immunisation programme & for risk groups
3/ JCVI took rather long to release their statement on vaccinating 12-17 yr-olds because risk-benefits of vaccinating this age-gp
were finely balanced between risk of severe #Covid19 & risk of rare but severe side-effects for the only vaccine licensed for 12-15 yr-olds (Pfizer)
Read 19 tweets
Shamez Ladhani Profile picture
21 Jul
1. Most of us do not really appreciate how resilient children and their immune systems are when they encounter #sarscov2. Most kids don’t even realize they have been exposed, which leads to ⬆️⬆️⬆️ over-estimation of the long-term effects of #COVID19 in children

Here’s why … 🧵
2/ when asked, most parents don’t even realize when they child was exposed to #SARS_CoV_2 because most kids either remain asymptomatic or have such a mild and transient illness that parents don’t even associate the illness with #COVID19
3/ In our primary schools study, although small numbers, parents reported no symptoms in 85% of kids who didn’t have #SARS_CoV_2 antibodies at start of the study & then developed antibodies during the study (ie. got infected) compared to 47% of staff
👉 thelancet.com/journals/lanch…
Read 7 tweets
Shamez Ladhani Profile picture
16 Jul
1/ We studied the quality,
quantity and persistence of #SARSCoV2 antibodies in primary school students (6-11 year-olds) compared to staff (adults) over 6 months (until ~7-8 months after their #SARSCoV2 infection)

Here’s what we found (pre-print) 🧵

👉 medrxiv.org/content/10.110…
2/ The proportion of students & staff who had #SARSCoV2 antibodies in back June 2020 was similar:

👉 11.5% (95%CI, 9.4-13.9) & 11.3% (95%CI, 9.2-13.6; p=0.88) students had nucleoprotein & RBD antibodies vs 15.6% (95%CI, 13.7-17.6) & 15.3% (95%CI, 13.4-17.3; p=0.83) staff
3/ Live virus neutralising activity (ability of antibody to kill #SARSCoV2) was detected in 79.8% (71/89) of N antibody & 85.5% (71/83) of RBD antibody positive kids. RBD correlated more strongly with neutralising activity (rs=0.75; p<0.0001) than N antibodies (rs=0.37; p<0.0001)
Read 7 tweets
Shamez Ladhani Profile picture
16 Jul
1/ We developed & validated an oral fluid assay to measure #SARSCoV2 antibodies. Basically it’s a lollipop stick with a sponge that collects oral fluid (saliva) from around cheeks/gums. Kids can do the test themselves & sample can be posted to the lab 🧵👉 medrxiv.org/content/10.110…
2/ Here’s the technical stuff: We used contemporaneous blood & oral fluid samples from ~2,000 kids & adults taking part in our school studies and developed 3 different oral fluid assays for testing & validating: N-antibody, Spike-antibody & RBD-antibody 👉 medrxiv.org/content/10.110…
3/ The N-protein capture assay was the best candidate, sensitivity 75% (95%CI, 71–79%) specificity 99% (95% CI: 78–99%) when compared with paired serum antibodies, but higher sensitivity in kids (80%, 95% CI: 71–88%) than adults (67%, CI: 60%-74%) 👉 medrxiv.org/content/10.110…
Read 5 tweets
Shamez Ladhani Profile picture
11 Jul
1/9. In England, #SARSCoV2 infection rates in school-aged kids & #COVID19 outbreaks have both ⬆️ in recent weeks (latest data 4 July) but that does not change the narrative on kids & their role in infection/transmission in school

Here’s why … 🧵

👉 assets.publishing.service.gov.uk/government/upl…
2/9. No one has claimed that kids don’t get infected or don’t transmit #SARSCoV2 to others. But the data suggest that lower risk with kids than adults. Eg. We don’t see two-thirds of staff/students infected in a single outbreak as we do in care homes 👉 thelancet.com/journals/eclin…
3/9. We & others have shown that #SARSCoV2 cases & outbreaks reflect community infection rates. Cases in kids generally follow adults *unless* adults are in lockdown & kids continue to go to school. This happened in Nov/Dec 2020 & Mar/Apr 2021. See👇👇

👉 journalofinfection.com/article/S0163-…
Read 9 tweets
Shamez Ladhani Profile picture
10 Jul
1/5. Mental health of Adolescents in the Pandemic: Long-COVID19 or Long-Pandemic Syndrome? (pre-print, thanks @MaryKRe)

Here’s another case-control study on long covid that measured #SARSCoV2 antibodies in teenagers

Here’s what they found … 🧵

👉 medrxiv.org/content/10.110…
2/5. 1560 kids (median age 15y):
- 188 (12%) seropositive (exposed to #SARSCoV2)
- 1365 (88%) seronegative (never exposed)

If you think this sample size is small, try bleeding 1500 teens!

They were asked the same questions ➡️ responses were near-identical in cases & controls
3/5. The authors did a subgroup analysis & found near-identical responses in teenagers who knew their #SARSCoV2 infection status vs those who didn’t

Yes, small samples size, but not even a signal of any difference in mental health status (see table👇)

👉 medrxiv.org/content/10.110…
Read 5 tweets

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