Covid Situation Report: May 2, 2024
Update on Covid providing information on positivity and hospital admissions for England and its regions. This post is best viewed using the browser or Substack app.
Introduction
This weekly Covid Situation report was originally posted on my substack ‘Seeing the Forest for the Trees’ where I publish articles on Covid and other topics. You can access my substack at the following link.
For those seeking more in-depth information, there is a topic of interest each week. This week's article examines the initial data released for the Spring 2024 booster campaign and summarises the main findings from a recent UKHSA report on the effectiveness of the Autumn 2023 booster.
Summary
This past week has seen some early signs that Covid levels are increasing across all regions and amongst those aged 65 years and older
There has been another rise in the Covid positivity rate this week, while the rates for Flu and RSV continued to fall. Nevertheless, the positivity rates for all these viruses remain relatively low.
Weekly hospital admission rates for Covid have increased slightly but continued to fall for Flu.
Over the past week, all regions have seen a small rise in weekly hospital admissions due to Covid, yet their rates continue to be low. Weekly hospitalisation rates increased most for those aged 65 years and older but remain relatively low.
UKHSA reported that the Autumn 2023 booster has markedly decreased hospitalisation risks for those aged 65 and above, although its efficacy diminishes 15 weeks after vaccination.
Considering the early signs of increasing, though still relatively low, Covid levels and the notable decline in vaccine efficacy after 15 weeks, a successful Spring 2024 booster campaign is important to protect the most vulnerable populations.
The good news is that the Spring 2024 booster campaign, which started on April 15, has got off to a great start with just over 1.3M doses given in the first two weeks!
As always, it’s important to remember that the risk of hospitalisation from Covid infection increases significantly with age and for those immunocompromised. Also ‘Long Covid’ remains a risk for all as shown by the recent ONS report. Therefore, it is prudent to take appropriate measures such as self-isolating when experiencing Covid symptoms and enhancing ventilation whenever possible.
Further analysis of the ONS data on Long Covid was covered in a recent article I posted which can be found here.
Status of main respiratory diseases in England
This section presents the latest data on positivity rates for primary respiratory infections in England. It is important to understand that positivity differs from prevalence, which refers to the overall percentage of COVID-19 in the general population. Appendix 1 provides a more detailed explanation of the difference and why positivity rates can be a useful proxy for Covid infection levels
The chart below displays the test positivity rates for the main respiratory illnesses in England, including Flu, Covid, RSV, and Rhinovirus.
There was a continued rise in the Covid positivity rate to 7.1% this week. The positivity rate for flu once again fell and is now well below that of Covid. Additionally, the rates for RSV continued to fall although there was a slight increase for Rhinovirus.
The following chart shows hospital admissions per 100,000 people in England for the main respiratory diseases.
Weekly hospital admission rates for Covid have started to increase although they are still at relatively low levels. Admissions for Flu continued on a downward trend.
The next panel chart in this section shows Covid hospital admissions per 100,000 people by region. Hover your cursor over one of the chart lines to display the admission rates for all regions.
Hospital admissions have risen across all regions, though they continue to be at relatively low levels.
The final panel chart in this section shows Covid hospital admissions per 100,000 people by age. Each panel represents one age group and the title and lines are colour coded. The grey lines show all of the other age groups to provide context.
While all age groups have experienced significant declines from the winter peak, weekly hospital admissions for individuals aged 65 and over are beginning to rise.
It's important to note that while testing policies have been updated from April 1, 2024, the guidelines for testing patients showing Covid symptoms or when a positive result would change the patient's treatment remained unchanged. Consequently, the number of Covid hospital admissions continues to be a dependable indicator of the virus's prevalence in the community for the period shown in these charts.
Covid hospital admissions and bed occupancy
This section gives a more detailed examination of the most recent daily Covid data for hospitals in England.
NHS England stopped the weekly publication of data used to create these dashboards from April 4, 2024. As a result, the next update of the daily Covid data for hospitals in England will be on May 9, 2024.
Autumn 2023 Booster vaccine effectiveness
Last week, the UKHSA released a COVID-19 vaccine surveillance report giving the results of a study in to the effectiveness of the Autumn 2023 booster campaign against hospitalisation for individuals 65 years and older.
Vaccine effectiveness is calculated by comparing the risk in the vaccinated and ‘unvaccinated’ groups, taking account of any differences in the two populations.
The UKHSA study included only individuals who had received at least two doses prior to their Autumn 2023 booster, with the last dose administered at least 12 weeks before. Consequently, the UKHSA analysis compared the risk between individuals fully vaccinated with the Autumn 2023 booster and those who had only received a booster in Autumn 2022 and Spring 2023. This means that the vaccine effectiveness measured is the incremental effectiveness on top of at least 12 weeks of waned protection.
The two vaccines offered were bivalent Original/Omicron BA.4-5 vaccine (Pfizer-BioNTech) and monovalent XBB.1.5 vaccine (Pfizer-BioNTech and Moderna). The bivalent BA.4-5 boosters were rolled out first, followed by the XBB boosters.
The table below illustrates the incremental vaccine effectiveness of the two available vaccines in preventing hospitalisations and how this effectiveness varied with the passage of time following the date the Autumn 2023 booster was given.
The incremental effectiveness against hospitalization for both booster vaccines reached approximately 50%; with the bivalent BA.4-5 boosters at 45.0% and the monovalent XBB.1.5 boosters at 54.8% at 2 to 4 weeks from vaccination. Since the confidence intervals for the two vaccines overlapped, there was no significant statistical difference between them.
Early evidence indicates a decline to approximately 17% incremental vaccine effectiveness at 15 weeks post-vaccination for the bivalent BA.4-5 doses. Sufficient data to estimate the incremental vaccine effectiveness at 15 weeks for the XBB.1.5 doses is not yet available.
To summarise, the Autumn 2023 booster has markedly decreased hospitalisation risks for those aged 65 and above, although its efficacy diminishes 15 weeks after vaccination.
Spring 2024 Booster Campaign
The Spring 2024 booster campaign for people aged 75 years and over, those in care homes, and individuals aged 6 months and over with a weakened immune system started an April 15.
Initial reports from NHS England indicated that the Spring 2024 booster campaign had got of the a good start. On their vaccination website they reported that:
As of Thursday 18 April 2024, over 3,400 adult care homes had already been visited, delivering over 48,400 vaccinations. An additional 6,400 vaccinations had been delivered to care home residents in other locations, such as their GP practice. More than 700,000 eligible individuals have booked an appointment to get their spring Covid-19 vaccine since the National Booking System opened on Monday 15 April 2024.
The chart below offers context by displaying the vaccine coverage for individuals aged 75 and older in England at the conclusion of each previous vaccination campaign.
The chart shows that vaccination coverage was very high for the initial course of three doses; however, it has fallen for the later booster campaigns, albeit still remaining at a high level. Furthermore, the coverage for the two Spring campaigns is less than that observed in the Autumn campaigns.
As there are early signs that the prevalence of Covid is starting to increase and vaccine effectiveness wanes significantly over 15 weeks it is important to have a successful Spring 2024 booster campaign to protect the most vulnerable.
The concluding chart displays the weekly number of doses administered during the booster campaigns to date. The Spring campaigns are represented in green, the Autumn campaigns in brown, and doses administered outside of these campaigns are depicted in grey.
The chart shows a clear difference between the Spring and Autumn campaigns. The Spring booster campaigns are limited to those aged 75 years and older, those in care homes, and individuals with a weakened immune system. NHS England estimated that about 7.3 million people are eligible for the Spring campaigns. The Autumn booster campaign's eligibility criteria vary by age and include hospital and care staff, individuals in care homes, and those with weakened immune systems. NHS England estimated that 26 million people were eligible for the Autumn 2022 campaign and 20 million for the Autumn 2023 campaign.
Finally, the Spring 2024 booster campaign has got off to a great start with just over 1.3M doses given in the first two weeks! You can check to see if you are eligible and book a booster at the following link.
In conclusion
Despite the reduced level of data, the available information indicates that Covid levels may have started to rise this week.
The Spring 2024 booster is in high demand among eligible individuals, with over 1.3 million doses administered in the first two weeks.
As always, if you have any comments on this Covid Situation Report or suggestions for topics to cover, please post a message below.
Appendix 1. Test positivity rates and prevalence
Positivity rates are derived from the results of hospital laboratory tests conducted on patients exhibiting symptoms of respiratory diseases. Test positivity is the percentage of patients who test positive for Covid of the total number of patients tested. Since the individuals tested for this measure are not a representative sample of the general population it differs from prevalence, which is derived from a representative sample of the population.
Test positivity rates, while not directly estimating the number of Covid infections in the general population, can be a valuable indicator of the infection trend. The panel chart below compares the weekly test positivity rate among hospital patients with respiratory symptoms to the prevalence of Covid in the general population, as reported in the Winter Infection Survey.
The chart shows that the weekly test positivity rates for patients with symptoms of respiratory infections follows the same pattern as the prevalence for Covid reported by the Winter Infection Survey. Since the Winter Infection Survey is based on a representative sample of the general population this supports using test positivity as a useful proxy for infection trends.
Thank you Bob. In your appendix you set out how positivity rate can be used as a proxy for general prevalence. Could you say a bit more about this? As a non statistician the graphs suggest to me that prevalence is around a half of the positivity rate. Is that pushing the data too far? For practical purposes in assessing my personal exposure risk over time it would be useful to have your guidance on this, in the absence of government survey data
You stress the importance of the Spring 2024 booster campaign to protect the most vulnerable but how effective is the XBB 1.5 vaccine which is being administered against the new JN.1 lineage? The WHO Technical Advisory Group on COVID-19 Vaccine Composition has advised the use of a monovalent JN.1 lineage as the antigen in future formulations of COVID-19 vaccines but I am not sure when this updated vaccine will become available.