Credit UK PHE/CMO
#16,132
Although we've been discussing the possibility since the spring (see UK To Begin New Clinical Trial On COVID `Booster' Vaccines), over the past couple of months we've seen numerous `red flags' (see here, here, and here) suggesting a 3rd `Booster shot' might be needed before the end of 2021.
Yesterday's Joint Statement from The HHS/CDC/FDA on plans to begin offering booster shots in late September - while a turnaround from their position of just over a month ago - was therefore not unexpected.
The primary benefit of the COVID vaccines has been - even with increasing breakthrough infections - that severe illness, hospitalization, and death among the fully vaccinated have been rare.
Included in yesterday's statement, however, was the following warning (bolding mine).
Based on our latest assessment, the current protection against severe disease, hospitalization, and death could diminish in the months ahead, especially among those who are at higher risk or were vaccinated during the earlier phases of the vaccination rollout.
While no specific cites for this particular assessment were offered, it seems likely that there are some sobering VE studies in the pipeline that support this statement.
Overnight, a new preprint came off embargo in the UK, which appears to contradict earlier studies suggesting the UK's extended gap between their 1st and 2nd vaccine dose (see UK Preprint: PITCH study – Antibody & Cellular Immune Responses after Two Different Dosing Schedules of the Pfizer Vaccine) may have increased the durability of vaccine protection.
This new paper by the University of Oxford, ONS and DHSC also finds - much as we saw reported from Israel in July - a sharp drop off of VE (Vaccine Effectiveness) in the UK (among Pfizer, Moderna & AstraZeneca recipients) beginning after 3 about months.
From the Nuffield Department of Medicine at the University of Oxford, we get the following summary, after which I'll have the link and abstract to the full paper and a link to some expect reaction published on the Science Media Centre website.
Key findings from the study:
- Obtaining two vaccine doses remains the most effective way to ensure protection against the COVID-19 Delta variant of concern dominant in the UK today.
- With Delta, Pfizer-BioNTech and Oxford-AstraZeneca vaccines still offer good protection against new infections, but effectiveness is reduced compared with Alpha.
- Two doses of either vaccine still provided at least the same level of protection as having had COVID-19 before through natural infection; people who had been vaccinated after already being infected with COVID-19 had even more protection than vaccinated individuals who had not had COVID-19 before.
- However, Delta infections after two vaccine doses had similar peak levels of virus to those in unvaccinated people; with the Alpha variant, peak virus levels in those infected post-vaccination were much lower.
Other findings:
- A single dose of the Moderna vaccine has similar or greater effectiveness against the Delta variant as single doses of the other vaccines.
- Two doses of Pfizer-BioNTech have greater initial effectiveness against new COVID-19 infections, but this declines faster compared with two doses of Oxford-AstraZeneca. Results suggest that after four to five months effectiveness of these two vaccines would be similar – however, long-term effects need to be studied.
- The time between doses does not affect effectiveness in preventing new infections, but younger people have even more protection from vaccination than older people.
Symptoms and SARS-CoV-2 positivity in the general population in the UK
Within the COVID-19 Infection Survey, recruiting representative households across the UK general population, SARS-CoV-2-associated symptoms varied by viral variant, vaccination status and demographics. However, differences are modest and do not currently warrant large-scale changes to targeted testing approach.
The full 39-page PDF may be accesses at:
Impact of Delta on viral burden and vaccine effectiveness against new SARS-CoV-2 infectionsin the UK
Koen B. Pouwels1,2 Emma Pritchard1,3 , Philippa C. Matthews3,5,6 , Nicole Stoesser1,3,5,6, David W. Eyre1,3,4,5 , Karina-Doris Vihta1,7 , Thomas House8,9 , Jodie Hay10,11 , John I Bell12 , John N Newton13 , Jeremy Farrar14 , Derrick Crook1,3,5,6, Duncan Cook15, Emma Rourke15, Ruth Studley15, Tim Peto1,3,5,6, Ian Diamond15, A. Sarah Walker1,3,5,16 and the COVID-19 Infection Survey Team
Abstract
The effectiveness of BNT162b2, ChAdOx1, and mRNA-1273 vaccines against new SARS-CoV-2 infections requires continuous re-evaluation, given the increasingly dominant Delta variant. We investigated the effectiveness of the vaccines in a large community-based survey of randomly selected households across the UK. We found that the effectiveness of BNT162b2 and ChAd0x1 against any infections (new PCR positives) and infections with symptoms or high viral burden is reduced with the Delta variant. A single dose of the mRNA-1273 vaccine had similar or greater effectiveness compared to a single dose of BNT162b2 or ChAdOx1.
Effectiveness of two doses remains at least as great as protection afforded by prior natural infection. The dynamics of immunity following second doses differed significantly between BNT162b2 and ChAdOx1, with greater initial effectiveness against new PCR-positives but faster declines in protection against high viral burden and symptomatic infection with BNT162b2. There was no evidence that effectiveness varied by dosing interval, but protection was higher among those vaccinated following a prior infection and younger adults. With Delta, infections occurring following two vaccinations had similar peak viral burden to those in unvaccinated individuals. SARS-CoV-2 vaccination still reduces new infections, but effectiveness and attenuation of peak viral burden are reduced with Delta.
You'll find an extended collection of expert reactions at:
AUGUST 19, 2021
Expert reaction to preprint looking at the impact of the delta variant on vaccine effectiveness
While the waning protection against the Delta variant by current vaccines is disappointing, these vaccines have undoubtedly saved hundreds of thousands of lives - and with the aid of booster shots - should continue to do so well into 2022.
The need for booster shots this soon does present significant logistical, and ethical, challenges.
Reportedly less than 1/3rd of the world's population has received their first shot, and just under 1/4th have received their 2nd, and most of these people reside in high or moderate income countries. Only 1.3% of those living in low income countries have been offered their first shot.
The problems of vaccine inequality, the logistics of global vaccine manufacturing and distribution, and the possibility of seeing vaccine escape viruses emerge are all topics we've covered before, albeit with more questions than answers.
A few examples include:
UK Sage: International Vaccination: Potential impact on Viral Evolution and UK
A COVID Vaccine Reality Check
MRC Report #33: Modelling The Allocation & Impact of a COVID-19 Vaccine
Manufacturing Pandemic Flu Vaccines: Easier Said Than Done
Multiple safe and effective vaccines were produced in less than a year, and nearly 5 billion doses have been administered over the past 9 months. Hundreds of thousands of lives have been saved, and many more severe illnesses and hospitalizations have been avoided.
