Public Health England

The latest Technical Briefing on the Variants of Concern, number 23, has been published by Public Health England (PHE), so we can update our (unadjusted) estimates of vaccine effectiveness against the Delta variant using the data it includes from sequenced Delta samples from positive PCR test results in England.

As before, we subtract the figures in the latest briefing, now no. 23, from those in briefing 17 to give the figures for the period June 22nd to September 12th. This gives us a picture for the whole Delta surge, which allows for the fact that most of the early reported infections were in the unvaccinated and most of the later reported infections were in the vaccinated (see below). PHE has recently also published the most recent month’s data for all reported infections (not just sequenced Delta ones), which shows lower vaccine efficacy in the most recent four weeks (a new report released on Friday shows this has dropped even further in the most recent week). However, given the apparently delayed infections in the vaccinated, it seems most accurate to look at the figures for the whole surge, not just the last month, when estimating vaccine efficacy against Delta.

We also use figures for proportions of the population vaccinated by age derived from the PHE Covid surveillance reports.

Starting with the over-50s, for the period June 22nd to September 12th, PHE reports 68,445 Delta infections in the double vaccinated and 7,575 in the unvaccinated. PHE figures show that in this period the proportion of the over-50s double vaccinated increased from 87% to 89%, giving a mean of 88%, and the proportion unvaccinated was stable at 9%. Calculating the vaccine effectiveness against Delta infection in the over-50s (1-(68,445/88%)/(7,575/9%)) gives a figure of just 7.6%. This is down from 15% two weeks ago and 24% two weeks before that. This continues to be very different to the estimate in the recent Oxford University study using ONS survey data, a study which I criticised for numerous inconsistent and implausible findings.

With regard to deaths with Covid (within 28 days of a positive test), PHE reports 1,515 in the double vaccinated and 552 in the unvaccinated in the over-50s in this period. This works out (1-(1,515/88%)/(552/9%)) at a vaccine effectiveness against death of 72%, down slightly from 74% using data from the previous briefing. This is a 72% reduction in mortality including any reduced risk of infection, not in addition to it. It continues to be an encouraging figure, albeit lower than earlier studies have suggested, and dropping week on week.

For the under-50s, for the period June 22nd to September 12th, PHE reports 81,718 Delta infections in the double vaccinated and 195,957 in the unvaccinated. PHE figures show that in this period the proportion of under-50s double vaccinated increased from 18% to 42%, giving a mean of 30%, and the proportion unvaccinated decreased from 61% to 50%, giving a mean of 55%. Calculating the vaccine effectiveness against Delta infection in the under-50s (1-(81,718/30%)/(195,957/55%)) gives a figure of 24%. This is down from 27% two weeks ago and 37% two weeks before that, and though higher than in the over-50s, is still very low and much lower than earlier studies (including the trial) indicated.

For deaths, PHE reports 48 in the double vaccinated and 126 in the unvaccinated in the under-50s in this period. This works out (1-(48/30%)/(126/55%)) at a vaccine effectiveness against death of 30%. This is up from 20% two weeks ago and 12% two weeks before that, but is still very low and much lower than in the over-50s. This may be because higher risk people are prioritised for vaccination, or are more likely to consent to it, in the younger age groups, and the rising efficacy may reflect the increase in lower risk people being vaccinated.

These figures are much lower than those commonly quoted and used in modelling, and if they are closer to the truth then they mean the official, self-congratulatory estimates of “100,000 deaths” and “24.4 million infections” prevented by the vaccines are huge overestimates.

By plotting the differences between the reported total Delta cases in the last five briefings we can also get a picture of how they are changing over time in the different age and vaccine-status cohorts. The red and yellow lines in the chart below show that new reported Delta infections in the unvaccinated have continued gently to increase, as have reported infections in the vaccinated over-50s (dark green line). On the other hand, new reported Delta infections in the vaccinated under-50s dropped in the last two weeks, driving an overall drop in reported Delta infections in the vaccinated. This may mark the peak of the Delta surge in the vaccinated, and possibly overall, though the gentle rise in reported infections in the unvaccinated since the start of August adds a smidgen of doubt into that inference.

Public Health England (PHE) published their latest weekly vaccine surveillance report on Thursday. Usually these just summarise other studies so are not particularly interesting, but this week something new appeared that has been widely asked for but elusive: data on cases, hospitalisations and deaths broken down by age and vaccination status.

Although the fortnightly technical briefings on the variants of concern have a breakdown of sequenced Delta cases broken down by vaccination status and into the over-50s and under-50s, this is the first time PHE has published general data on all cases (not just sequenced ones) split up by age and vaccination status.

The data comes from the Second Generation Surveillance System (SGSS), the relationship of which to the Government dashboard data is unclear, though the figures are similar. It reports 722,728 cases in the reporting period, compared to the dashboard figure of 727,010 by specimen date, so this seems comprehensive. On the other hand, it includes 6,605 hospitalisations, whereas the dashboard has 21,242, more than three times as many, though this may be due to how it counts hospitalisations (“Cases whom [sic] presented to emergency care (within 28 days of a positive specimen), resulting in overnight inpatient admission”). It has 2,381 deaths, against the dashboard’s 2,496, so again this is most of them.

It is just data for the past month, August 9th to September 5th. We can use it to calculate a rough estimate of unadjusted vaccine effectiveness in different age cohorts for this four-week period.

Vaccines Have NEGATIVE Effectiveness in the Over-40s, as Low as MINUS 38%, Shows New PHE ReportRead More

The latest Technical Briefing on the variants of concern, number 22, has been published by Public Health England (PHE), so we can update our (unadjusted) estimates of vaccine effectiveness against the Delta variant using the data it includes from sequenced Delta samples from positive PCR test results in England.

As before, we subtract the figures in briefing 22 from those in briefing 17 to give the figures for the period June 22nd to August 29th. We also use figures for proportions of the population vaccinated by age derived from the PHE Covid surveillance reports.

Starting with the over-50s, for the period June 22nd to August 29th, PHE reports 47,874 Delta infections in the double vaccinated and 5,748 in the unvaccinated. PHE figures show that in this period the proportion of the over-50s double vaccinated increased from 87% to 89%, giving a mean of 88%, and the proportion unvaccinated was stable at 9% (Note: not 10% as I stated previously). Calculating the vaccine effectiveness against Delta infection in the over-50s (1-(47,874/88%)/(5,748/9%)) gives a figure of 15%. This is the same as the figure I calculated two weeks ago, though now using the more accurate figure of 9% rather than 10% for the proportion unvaccinated. This means that it represents a decline (using 9% for the previous calculation would give a VE of 24%). This continues to be very different to the estimate in the recent Oxford University study using ONS survey data, a study which I criticised for numerous inconsistent and implausible findings.

With regard to deaths with Covid (within 28 days of a positive test), PHE reports 1,004 in the double vaccinated and 399 in the unvaccinated in the over-50s in this period. This works out (1-(1,004/88%)/(399/9%)) at a vaccine effectiveness against death of 74%, down slightly from 75% using data from the previous briefing (even with the change to 9% unvaccinated). This is a 74% reduction in mortality including any reduced risk of infection, not in addition to it. It continues to be an encouraging figure, albeit lower than earlier studies have suggested, and dropping week on week.

For the under-50s, for the period June 22nd to August 29th, PHE reports 58,714 Delta infections in the double vaccinated and 160,143 in the unvaccinated. PHE figures show that in this period the proportion of under-50s double vaccinated increased from 18% to 39%, giving a mean of 28%, and the proportion unvaccinated decreased from 61% to 51%, giving a mean of 56%. Calculating the vaccine effectiveness against Delta infection in the under-50s (1-(58,714/28%)/(160,143/56%)) gives a figure of 27%. This is down from 37% two weeks ago, and though higher than in the over-50s, is still very low and much lower than earlier studies (including the trial) indicated.

For deaths, PHE reports 37 in the double vaccinated and 93 in the unvaccinated in the under-50s in this period. This works out (1-(37/28%)/(93/56%)) at a vaccine effectiveness against death of 20%. This is up from 12% two weeks ago, but is still very low and much lower than in the over-50s. This may be because higher risk people are prioritised for vaccination, or are more likely to consent to it, in the younger age groups.

These figures are much lower than those commonly quoted and used in modelling, and if they are closer to the truth then they mean the official, self-congratulatory estimates of “100,000 deaths” and “24.4 million infections” prevented by the vaccines are huge overestimates.

By plotting the differences between the reported total Delta cases in the last four briefings we can also get a picture of how they are changing over time in the different age and vaccine-status cohorts. The red and yellow lines in the chart below show that new Delta infections in the unvaccinated have started to increase again, but not by as much as those in the vaccinated (for this purpose, all who are at least 21 days after their first dose), which have continued to surge. A majority of new infections (57,565 out of 94,148, or 61%) are now in the vaccinated. This means that the recent increase in reported infections in England is being driven primarily by infections in the vaccinated. The fainter lines show the trends in the over- and under-50s, indicating that in both age cohorts new Delta infections in the vaccinated now outnumber those in the unvaccinated, and that new infections in the vaccinated over-50s are increasing particularly fast. This helps to explain the declining vaccine effectiveness estimates given above.

Public Health England (PHE) has released a new technical briefing on the variants of concern, number 21, and this allows us to update our estimate of (unadjusted) vaccine effectiveness against the Delta variant using the data it provides on confirmed Delta cases.

We subtract the figures in briefing 21 from those in briefing 17 to give the figures for the period June 22nd to August 15th. We also use figures for proportions of the population vaccinated by age derived from the PHE Covid surveillance reports.

Starting with the over-50s, for the period June 22nd to August 15th, PHE reports 29,282 Delta infections in the double vaccinated and 3,915 in the unvaccinated. PHE figures show that in this period the proportion of the over-50s double vaccinated was stable at 88% and the proportion unvaccinated was 10%. Calculating the vaccine effectiveness against Delta infection in the over-50s (1-(29,282/88%)/(3,915/10%)) gives a figure of just 15%, down from 17% using data from the briefing two weeks ago. This is very different to the estimate in the recent Oxford University study using ONS survey data, a study which I criticised for numerous implausible findings.

With regard to deaths with Covid (within 28 days of a positive test), PHE reports 602 in the double vaccinated and 280 in the unvaccinated in the over-50s in this period. This works out (1-(602/88%)/(280/10%)) at a vaccine effectiveness against death of 76%, down slightly from 77% using data from the previous briefing. This is a 76% reduction in mortality including any reduced risk of infection, not in addition to it. It’s an encouraging figure, albeit lower than earlier studies have suggested.

For the under-50s, for the period June 22nd to August 15th, PHE reports 36,855 Delta infections in the double vaccinated and 125,394 in the unvaccinated. PHE figures show that on June 20th 61% of under-50s were unvaccinated while 18% were double vaccinated. On August 15th those figures were 52% unvaccinated and 35% double vaccinated. Taking the average of these gives 56% unvaccinated and 26% double vaccinated for the period. Using this to calculate the vaccine effectiveness against Delta infection in the under-50s (1-(36,855/26%)/(125,394/56%)) gives a figure of 37%. This is higher than in the over-50s, but still very low and much lower than earlier studies (including the trial) indicated.

For deaths, PHE reports 27 in the double vaccinated and 66 in the unvaccinated in the under-50s in this period. This works out (1-(27/26%)/(66/56%)) at a vaccine effectiveness against death of just 12%. Why this would be so much lower than in the over-50s is unclear, but it’s worth bearing in mind that these are small numbers of deaths which may make the estimate unreliable.

These figures are much lower than those commonly quoted and used in modelling, and if they are closer to the truth then they mean the official, self-congratulatory estimates of “100,000 deaths” and “24.4 million infections” prevented by the vaccines are huge overestimates.

By plotting the differences between the reported total Delta cases in the last three briefings we can also get a picture of how they are changing over time in the different age and vaccine-status cohorts. The red and yellow lines in the chart below show that new Delta infections in the unvaccinated have stayed largely flat over the past fortnight, but those in the vaccinated (for this purpose, all who are at least 21 days after their first dose) have surged, so that a majority of new infections (44,038 out of 76,117, or 58%) are now in the vaccinated. This reveals that the recent modest increase in positive cases in England is being driven primarily by infections in the vaccinated. The fainter lines show the trends in the over- and under-50s, indicating that in both age cohorts new Delta infections in the vaccinated now outnumber those in the unvaccinated. This helps to explain the declining vaccine effectiveness estimates given above.