Credit Imperial College London
#16,103
In a perfect world, getting vaccinated against COVID would provide complete, long-lasting protection against infection with SARS-CoV-2, and the pandemic would swiftly fade away. That scenario, however, only happens in the movies or other works of fiction.
Pandemics are far more complicated, and their remedies are more nuanced, in the real world.
While there is ample evidence that being fully vaccinated against COVID provides excellent protection against serious illness, hospitalization, and death - the things that should concern us most - we are seeing evidence of increasing breakthrough infections in the vaccinated due to rising variants, and hints that the earliest recipients of the vaccine may be losing some of their protection.
A few, of many, recent examples include:
The CDC `The War Has Changed' Internal Document On Delta Variant
UK Preprint: PITCH study – Antibody & Cellular Immune Responses after Two Different Dosing Schedules of the Pfizer Vaccine
UK: Updated Risk Assessments On COVID Delta & Beta Variants
EID Journal: Breakthrough Infections of SARS-CoV-2 Gamma Variant in Fully Vaccinated Gold Miners, French Guiana, 2021
Convincing a weary and skeptical public - one which is constantly being inundated with anti-vaccine propaganda - that a less than perfect vaccine, is still a good vaccine - isn't easy.
Particularly when the latest pandemic news isn't all unicorns and rainbows.
Which brings us to the latest REACT-1 preprint, published today, which finds that vaccine protection against symptomatic infection in the UK may be significantly lower with the Delta variant than previously reported against Alpha:
(Excerpt)
The rapid growth across and within rounds appears to have been driven by complete replacement of Alpha variant by Delta, and by the high prevalence in younger less-vaccinated age groups, with a nine-fold increase between rounds 12 and 13 among those aged 13 to 17 years
Prevalence among those who reported being unvaccinated was three-fold higher than those who reported being fully vaccinated. However, in round 13, 44% of infections occurred in fully vaccinated individuals, reflecting imperfect vaccine effectiveness against infection despite high overall levels of vaccination.
Using self-reported vaccination status, we estimated adjusted vaccine effectiveness against infection in round 13 of 49% (22%, 67%) among participants aged 18 to 64 years, which rose to 58% (33%, 73%) when considering only strong positives (Cycle threshold [Ct] values < 27); also, we estimated adjusted vaccine effectiveness against symptomatic infection of 59% (23%, 78%), with any one of three common COVID-19 symptoms reported in the month prior to swabbing.
While still a largely positive finding - it likely won't match the expectations of the public - which is more accustomed to hearing about the 90% effectiveness number (albeit, against hospitalization, serious illness, and death) used in promoting the jab.
Hence the alternative headline descriptor from the DHSC press release (below) of the fully vaccinated being `3 times less likely to be infected'. Both reflect findings from this report, but one sounds far better than the other.
First the press release, then I'll return with more from the actual preprint.
REACT study shows fully vaccinated are three times less likely to be infected
The latest REACT-1 study findings from Imperial College London and Ipsos MORI show COVID-19 infection rates are three times lower for double vaccinated people.Published 4 August 2021
- Findings covering 24 June to 12 July from Imperial College London and Ipsos MORI show fully vaccinated people were three times less likely than unvaccinated people to test positive for COVID-19
- Ministers urge caution as society opens up, with some fully vaccinated people still able to test positive
- Study shows infections have increased four-fold compared to the last report in late May, with 1 in 160 people infected, although growth appeared to be slowing
Findings from the latest report of REACT-1, one of the country’s largest studies into COVID-19 infections in England, have been published today (Wednesday 4 August) by Imperial College London and Ipsos MORI.Over 98,000 volunteers took part in the study in England between 24 June and 12 July to examine the levels of COVID-19 in the general population. The latest data show infections in England have increased fourfold from 0.15% to 0.63% since the last REACT-1 report which covered the period 20 May to 7 June.Despite this increase, the findings indicate the spread of the virus was slowing as of 12 July and infection rates for double vaccinated people are three times lower than in unvaccinated.Analysis by Imperial College suggests double vaccinated people are also less likely to pass on the virus to others.The main findings from the thirteenth round of the REACT-1 study show:
- 527 positives from 98,233 swabs, giving a prevalence of 0.63% or 1 in 160 people;
- more than a four-fold rise in prevalence compared to the last full report which covered 20 May-7 June, increasing from 0.15% to 0.63;
- unvaccinated people were three times more likely than fully vaccinated people to test positive for COVID-19, with prevalence at 1.21% and 0.40%;
- double vaccinated people in the most recent round were estimated to have around 50 to 60% reduced risk of infection, including asymptomatic infection, compared to unvaccinated people;
- those who were fully vaccinated may be less likely to pass on the virus to others than those who have not received a vaccine;
- prevalence was highest in London at 0.94%, up from 0.13% in round 12, although this growth appeared to be slowing at the end the study period;
- during Round 13, the R number was estimated at 1.19, corresponding to a doubling time of 25 days;
- of the 254 positive samples sequenced for variants, 100% were the Delta variant, compared to 78.3% in the last report at the end of May (round 12);
- a substantial increase in prevalence in all age groups under the age of 75;
- prevalence is nine-fold higher in 13-17 year-olds at 1.56% compared with 0.16% in round 12;
- 3.84% of double-vaccinated individuals who reported recent contact with a known COVID-19 case tested positive, compared to 7.23% of unvaccinated individuals; and
- when comparing the REACT infection data with official NHSE hospitalisation data, since mid-February there has been a weakening in the relationship between infections and hospitalisations and deaths. Since mid-April there are signs of the relationship between infections and hospitalisations coming back together. More time is needed to understand what this means and to identify any trends.
The vaccination programme has been successful in weakening the link between infection, hospitalisation and deaths and today’s data demonstrates the need to remain vigilant and follow government guidance, to ensure that we continue to reduce the risk.Data from Public Health England (PHE) shows our vaccines are highly effective against all variants of COVID-19. The Pfizer/BioNTech vaccine is 96% effective and the Oxford/AstraZeneca vaccine is 92% effective against hospitalisation after both doses. PHE estimates that the vaccination programme in England has prevented 22 million infections, around 52,600 hospitalisations and between 35,200 and 60,000 deaths.PHE hospitalisation data shows that between 21 June and 19 July, 1,788 people were admitted to hospital after testing positive for the Delta variant. Of these, 970 (54.3%) were unvaccinated, while 530 (29.6%) had received both doses of the vaccine. In total, 3,692 people have been hospitalised with the delta variant, of whom 2,152 (58.3%) were unvaccinated and 843 (22.8%) were fully vaccinated. The latest PHE risk assessment for the Delta variant reflects early signs of increased risk of reinfection with Delta compared to Alpha. Further investigations are being undertaken by PHE and data will be updated on Friday.There are around 2.8 million 18-29-year olds who are completely unvaccinated. While the risk of getting seriously ill is lower among this group, it is becoming increasingly clear that individuals who are unvaccinated and catch the virus are more likely to pass it on to others, including those who are more vulnerable, when compared to someone who is fully vaccinated.
The authors of the preprint go on to say:
That Israeli data from late July found very low (41%) protection against symptomatic infection by the Delta Variant from the Pfizer vaccine, which was in stark contrast to what the UK had previously reported (88%).Our estimate of vaccine effectiveness against all SARS-CoV-2 infections for two doses of vaccine was 49% in the most recent data, increasing to 58% when we defined effectiveness only for strong positives. These estimates are lower than some others [15,17,18], but consistent with more recent data from Israel [19]
Granted, since the absolute number of infected individuals picked up by this survey was small, these results may not fully reflect the effectiveness of the vaccine. You'll find several (very long) explanations on the limitations of this study on the Science Media Centre's expert reaction to this study.
The authors go on to warn that:
In conclusion, we have shown rapid exponential growth of SARS-CoV2 prevalence during the third wave in England at a time when Delta variant became dominant. The rapid roll-out of the vaccination programme in England has so far limited the number of infections and serious cases relative to the unvaccinated population.
Level or declining prevalence may be observed during the summer in the northern hemisphere, reflecting school vacations, greater time spent outdoors and reduced social interactions. But without additional interventions, increased mixing during the autumn in the presence of Delta variant may lead to renewed growth, even at high levels of vaccination. Continued surveillance to monitor the spread of the epidemic is therefore required.
Lower VE estimates or not, it is far better to be fully vaccinated against COVID, as your chances of having serious illness, being hospitalized, or dying are greatly reduced.
But there is growing evidence suggesting that the current vaccines are less effective against infection with Delta, and that for early recipients, the vaccine's protection may be waning.
This may not be the unambiguously positive public health message that most governments want to deliver, but it is the reality of this pandemic. And one we have to accept, if we are to make the adjustments needed to successfully navigate the remainder of this pandemic.
