Pneumococcal Polysaccharide Vaccine (PPV) coverage report, England, April 2021 to March 2022
Updated 1 May 2024
Applies to England
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Summary
The current report presents analyses using GP-level data from 10,475,904 individuals aged 65 years and over and 3,870,876 individuals aged 2 to 64 years in 9 clinical risk groups, who were registered with 6,242 GPs in England on 31 March 2022.
Coverage was defined as the proportion of GP-registered individuals, as of 31 March 2022, who were:
- 65 years and over, or
- aged 2 to 64 years and in one or more clinical risk groups
and who had received PPV any time on or before 31 March 2022.
Uptake was defined as the proportion of GP-registered individuals, as of 31 March 2022, who were:
- 65 years and over, or
- aged 2 to 64 years and in one or more clinical risk groups
who received PPV between 1 April 2021 and 31 March 2022.
Coverage among individuals aged 65 years and over was estimated at 71.5% (men 71.1%, women 71.8 %), which was 0.9 percentage points higher than in 2020 to 2021. Coverage ranged from 67.5 % in the London commissioning region to 73.4 % in the North East and Yorkshire commissioning region.
Coverage increased from 33.0 % in the youngest age group (65 years) to 83.6 % in the oldest age group (75 years and over). Coverage was between 0.02 and 1.4 percentage points higher than in 2020 to 2021 across age groups, except among individuals aged 65 years, among whom coverage was 1.2 percentage points lower than in 2020 to 2021.
Uptake was estimated at 4.8 % among individuals aged 65 years and over compared to 4.9 % in 2020 to 2021. Uptake ranged from 4.4 % in the South West commissioning region to 5.9 % in the London commissioning region.
Uptake decreased from 13.4 % in the youngest age group (age 65 years) to 2.2 % in the oldest age group (75 years and over). Compared to 2020 to 2021, uptake was between 0.7 and 1.7 percentage points lower in age groups between 65 years and 69 years, whereas uptake was 0.4 to 0.5 percentage points higher among individuals aged 70 to 74 years and 75 years and over than in 2020 to 2021.
Vaccine coverage among individuals aged 2 to 64 years in one or more clinical risk groups was 46.2% (women 46.4 %, men 46.0 %).
Coverage in individual clinical risk groups ranged from 39.5 % (chronic liver disease) to 70.5 % (cochlear implants). The greatest percentage points difference in coverage among clinical risk groups since last year was observed for Asplenia or dysfunction of the spleen, which increased by 6.8 percentage points to 45.9 % in the current year. Differences in coverage since last year among individuals in the remaining clinical risk groups ranged from a decrease of 0.2 percentage points (cochlear implants) to an increase of 2.1 percentage points (cerebrospinal fluid leaks).
Vaccine uptake among individuals in one or more clinical risk group was 5.5 % (women 5.5 %, men 5.4 %). The current report did not compare uptake among individuals in one or more risk groups to last year’s figures or report on vaccine uptake in individual clinical risk groups due to data quality issues.
Introduction
This report describes vaccine coverage and uptake of the pneumococcal polysaccharide vaccine (PPV) programme in England. The current collection included data from adults aged 65 years and over and individuals aged 2 to 64 years in 9 clinical risk groups associated with elevated risk of adverse outcomes of pneumococcal disease (1). The current report presents vaccine coverage and uptake estimates for the period between 1 April 2021 to 31 March 2022, and compares them to the previous year (1 April 2020 to 31 March 2021) (2).
Pneumococcal disease can present as non-invasive or invasive infections caused by the bacterium Streptococcus pneumoniae (also called pneumococcus). Non-invasive disease includes middle ear infections (otitis media), sinusitis and bronchitis, whilst invasive pneumococcal disease (IPD) includes septicaemia, pneumonia and meningitis.
IPD is a significant cause of morbidity and mortality globally and in the UK with more than 5,000 confirmed cases reported in 2016 to 2017 in England and Wales (3). Pneumococcal immunisation is currently offered to young children, the elderly (people aged 65 years and over) and individuals with certain medical conditions because these groups are at the highest risk of IPD (1).
Pneumococcal immunisation has been recommended for clinical risk groups since 1992 (1). The pneumococcal immunisation programme was introduced in the UK in August 2003 and offered a single dose of PPV to people aged 80 years and over in addition to those at high risk under 65 years of age (4), (5). In April 2004, the programme was expanded to include all people aged 75 years and over. Since April 2005, all people aged 65 years and over have been eligible for PPV.
PPV (also currently known as PPV23) is an inactivated vaccine that contains purified polysaccharide from 23 capsular pneumococcus types, including the 10 most prevalent serotypes: 14, 9V, 1, 8, 23F, 4, 3, 6B, 19F, 7F. Most healthy adults develop a good antibody response to a single dose of PPV (1). Among people aged 65 years and over, PPV offers moderate short-term protection against IPD caused by the 23 serotypes targeted by the vaccine (6). In contrast, children younger than 2 years of age show poor antibody response to vaccination with PPV and there is no evidence to support effectiveness of the vaccine among this population group (1). Children younger than 2 years of age are therefore offered a pneumococcal conjugate vaccine (PCV13) through the childhood immunisation programme. Further information on PPV vaccine eligibility is available in the ‘Immunisation against infectious disease’ book (1).
In response to the COVID-19 pandemic, nationwide social distancing measures were initiated from 23 March 2020 and specific guidance for elderly and vulnerable groups to temporarily shield were in place throughout the pandemic (7), which might have disrupted the delivery of the PPV vaccination programme.
Methods
The current report presents coverage and uptake estimates among GP-registered individuals in England who were eligible for PPV because of either being 65 years of age and over, or aged 2 to 64 years and in a clinical risk group.
GP IT suppliers used a standardised script (developed by UKHSA and PRIMIS) to automatically extract GP-level data from medical records of individuals, who were registered with a GP in England on the last day of the collection period, 31 March 2022.
The number of individuals registered with the GP and the number of individuals vaccinated with PPV were captured by age group, clinical risk group, and gender.
Age, gender and clinical risk groups of the data used for this report
The age, gender and clinical risk groups of the data used for this report are as follows:
Age groups
- 65 years
- 66 years
- 67 years
- 68 years
- 69 years
- 70 to 74 years
- 75 years and over
- total (65 years and over)
Clinical risk groups
- asplenia
- chronic respiratory disease
- chronic heart disease
- chronic kidney disease
- chronic liver disease
- diabetes requiring insulin or oral hypoglycaemic medication
- immunosuppression
- cochlear implants
- cerebrospinal fluid leak
Gender groups
- men
- women
- gender not specified
- gender not known
- total (all genders)
All data was aggregated by GP, NHS England Clinical Commissioning Group (CCG), Sustainability and Transformation Partnerships (STP) and NHS commissioning region, and uploaded to the secure online platform, ImmForm, where it was accessed by UKHSA for analysis. UKHSA validated the data using analytical and visual inspections and queried any outliers or anomalous results with data providers before producing the results presented in the current report.
Definitions of ‘uptake’ and ‘coverage’
Uptake and coverage estimates were calculated using the following definitions:
Vaccine coverage among individuals aged 65 years and over
This is the percentage of GP-registered individuals who were 65 years and over on 31 March 2022 and who received PPV any time on or before 31 March 2022.
Vaccine uptake among individuals aged 65 years and over
This is the percentage of GP-registered individuals who were 65 years and over on 31 March 2022 and who received PPV between 1 April 2021 and 31 March 2022.
Vaccine coverage among individuals aged 2 to 64 years in individual clinical risk groups
This is the percentage of GP-registered individuals, who were 2 to 64 years on 31 March 2022, who were in clinical risk groups any time on or before 31 March 2022, and who received PPV any time on or before 31 March 2022.
Vaccine coverage among individuals aged 2 to 64 years in one or more clinical risk groups
This is the percentage of GP-registered individuals, who were 2 to 64 years on 31 March 2022, who were in one or more clinical risk groups any time on or before 31 March 2022, and who received PPV any time on or before 31 March 2022.
Vaccine uptake among individuals aged 2 to 64 years in one or more clinical risk group
This is the percentage of GP-registered individuals, who were 2 to 64 years on 31 March 2022, who became at risk in one or more risk groups between 1 April 2021 and 31 March 2022, and who received PPV between 1 April 2021 and 31 March 2022.
Estimates of vaccine coverage and uptake among individuals aged 65 years and over are presented overall and by age group and gender. Estimates of vaccination coverage and uptake among individuals aged 2 to 64 years in one or more clinical risk groups are presented overall and by gender. Vaccination coverage among individuals aged 2 to 64 years is further presented by individual clinical risk groups. It should be noted that individuals in individual risk groups are counted in each individual group and that the sum of individuals across clinical risk groups does not directly compare to the overall and gender separated estimates, for which individuals in more than one risk groups were counted only once.
Supplementary tables with estimates by CCG, STP and NHS commissioning region are published separately in the data appendix associated with this report.
Vaccine uptake for individuals aged 2 to 64 in individual clinical risk groups, and the percentage of individuals who declined or refused vaccines, are excluded due to data quality issues.
Results
Response summary
All 3 GP IT suppliers provided data. Of 6,438 GP practices in 2021 to 2022, 6,288 (97.7%) provided data. Due to data quality issues, 46 GP practices from one IT supplier were excluded from analysis. The analysis was performed using GP-level aggregated data from 6,242 GPs, which included 10,475,904 people aged 65 years and over and 3,870,876 individuals, who were in one or more clinical risk groups.
Coverage and uptake among individuals aged 65 years and over
PPV coverage by age group
Coverage was estimated at 71.5 % among individuals aged 65 years and over (Table 1). Coverage increased across groups of individuals of increasing age, from the youngest individuals aged 65 years of age (33.0%) to individuals aged 75 years and over (83.6 %).
Table 1. Estimated vaccine coverage, uptake and differences in estimated coverage and uptake since 2020 to 2021 among GP-registered individuals aged 65 years and over, as of 31 March 2022, by age group in England
| Age group | GP-registered individuals on 31 March 2022 | Estimated PPV uptake | Difference in estimated PPV uptake since 2020 to 2021 (%) | Estimated PPV coverage | Difference in estimated PPV coverage since 2020 to 2021 (% difference) |
|---|---|---|---|---|---|
| 65 years | 605,412 | 13.4 | -1.7 | 33.0 | -1.2 |
| 66 years | 577,327 | 11.5 | -1.7 | 45.2 | 0.02 |
| 67 years | 559,086 | 8.1 | -1.5 | 52.7 | 1.2 |
| 68 years | 555,633 | 6.7 | -1.3 | 57.6 | 1.2 |
| 69 years | 535,419 | 5.9 | -0.7 | 61.7 | 1.2 |
| 70 to 74 years | 2,677,214 | 5.0 | 0.4 | 72.1 | 1.4 |
| 75 years and over | 5,002,436 | 2.2 | 0.5 | 83.5 | 0.6 |
| Total | 10,512,527 | 4.8 | -0.1 | 71.5 | 0.9 |
Vaccine coverage was higher in the current reporting period than in 2020 to 2021 among individuals aged 65 years and over (0.9 percentage points) as well as in most age groups, ranging from 0.02 percentage points (66 years) to 1.4 percentage points (70 to 74 years) (Table 1). In contrast, coverage was 1.2 percentage points lower in the youngest age group (65 years) compared to 2020 to 2021.
PPV uptake by age group
Uptake was estimated at 4.8 % among all individuals aged 65 years and over. Uptake decreased with each increase in age group, from an estimated 13.4 % among people aged 65 years to 2.2 % among people aged 75 years and over (Table 1).
Uptake was 0.1 percentage points lower among individuals aged 65 years and over in the current reporting period than in 2020 to 2021 (Table 1). Uptake was lower than in 2020 to 2021 in age groups between 65 years to 69 years (range: 0.7 percentage points lower (69-year-olds) to 1.7 percentage points lower (65 and 66-year-olds)). In contrast, uptake was 0.4 percentage points higher among individuals aged 70 to 74 years and 0.5 percentage points higher among individuals aged 75 years and over than in 2020 to 2021.
PPV coverage and uptake by age group and geography
Overall coverage and uptake (individuals aged 65 years) as well as coverage and uptake for individual age groups varied across the 7 NHS commissioning regions (Table 2). (Estimates by CCG, STP and NHS commissioning region are available in the data appendix associated with this report.
Estimated coverage was highest in in the North East and Yorkshire commissioning region (73.4 %) and lowest in the London commissioning region (67.5 %). Estimated uptake was highest in the London commissioning region (5.9 %) and lowest in the South West commissioning region (4.4 %).
The patterns of coverage and uptake estimates by age group in each of the commissioning regions followed the trend of the age separated analysis for England as a whole. That is, coverage was lowest in the youngest age group (65 years) and increased with each increase in age group in all commissioning regions. In contrast, uptake estimates were highest among the youngest group (65 years) and decreased across age groups in all commissioning regions.
Table 2. Vaccine coverage and uptake among GP-registered individuals aged 65 years and over, as of 31 March 2022, by age group and NHS clinical commissioning region in England
East of England commissioning region
| Age group | GP-registered individuals on 31 March 2022 | Estimated PPV uptake (%) | Estimated PPV coverage (%) |
|---|---|---|---|
| 65 years | 72,212 | 13.6 | 30.9 |
| 66 years | 69,372 | 11.6 | 41.7 |
| 67 years | 67,809 | 8.1 | 49.1 |
| 68 years | 66,967 | 6.6 | 54.2 |
| 69 years | 65,171 | 5.9 | 58.8 |
| 70 to 74 years | 331,895 | 5.0 | 71.1 |
| 75 years and over | 637,292 | 2.0 | 83.8 |
| Total | 1,310,718 | 4.6 | 70.9 |
London commissioning region
| Age group | GP-registered individuals on 31 March 2022 | Estimated PPV uptake (%) | Estimated PPV coverage (%) |
|---|---|---|---|
| 65 years | 76,252 | 12.9 | 32.6 |
| 66 years | 71,708 | 11.5 | 44.7 |
| 67 years | 67,237 | 8.7 | 51.1 |
| 68 years | 63,493 | 7.3 | 55.7 |
| 69 years | 60,533 | 6.8 | 59.8 |
| 70 to 74 years | 276,317 | 6.2 | 68.4 |
| 75 years and over | 493,295 | 3.1 | 80.4 |
| Total | 1,108,835 | 5.9 | 67.5 |
Midlands commissioning region
| Age group | GP-registered individuals on 31 March 2022 | Estimated PPV uptake (%) | Estimated PPV coverage (%) |
|---|---|---|---|
| 65 years | 115,033 | 13.5 | 33.3 |
| 66 years | 110,084 | 11.6 | 45.0 |
| 67 years | 107,026 | 8.0 | 52.8 |
| 68 years | 108,126 | 6.7 | 57.4 |
| 69 years | 104,477 | 5.9 | 61.2 |
| 70 to 74 years | 521,568 | 4.9 | 71.9 |
| 75 years and over | 976,888 | 2.2 | 83.3 |
| Total | 2,043,202 | 4.7 | 71.4 |
North East and Yorkshire commissioning region
| Age group | GP-registered individuals on 31 March 2022 | Estimated PPV uptake (%) | Estimated PPV coverage (%) |
|---|---|---|---|
| 65 years | 99,975 | 14.6 | 36.2 |
| 66 years | 95624 | 11.5 | 48.5 |
| 67 years | 91,809 | 7.8 | 55.9 |
| 68 years | 92,197 | 6.4 | 61.1 |
| 69 years | 88,375 | 5.6 | 64.6 |
| 70 to 74 years | 442,367 | 4.6 | 74.5 |
| 75 years and over | 789,657 | 1.9 | 84.9 |
| Total | 1,700,004 | 4.7 | 73.4 |
North West commissioning region
| Age group | GP-registered individuals on 31 March 2022 | Estimated PPV uptake (%) | Estimated PPV coverage (%) |
|---|---|---|---|
| 65 years | 76,914 | 13.3 | 35.7 |
| 66 years | 72,804 | 11.6 | 48.6 |
| 67 years | 70,101 | 8.3 | 56.8 |
| 68 years | 70,226 | 7.0 | 61.2 |
| 69 years | 67,355 | 6.0 | 65.5 |
| 70 to 74 years | 336,393 | 5.1 | 73.8 |
| 75 years and over | 603,291 | 2.4 | 84.3 |
| Total | 1,297,084 | 5.0 | 73.0 |
South East commissioning region
| Age group | GP-registered individuals on 31 March 2022 | Estimated PPV uptake (%) | Estimated PPV coverage (%) |
|---|---|---|---|
| 65 years | 96,543 | 12.6 | 30.2 |
| 66 years | 92,067 | 11.6 | 43.1 |
| 67 years | 90,574 | 8.1 | 51.3 |
| 68 years | 88,921 | 6.7 | 56.8 |
| 69 years | 86,053 | 5.9 | 61.8 |
| 70 to 74 years | 442,130 | 5.0 | 72.2 |
| 75 years and over | 871,781 | 2.2 | 83.9 |
| Total | 1,768,069 | 4.6 | 71.8 |
South West commissioning region
| Age group | GP-registered individuals on 31 March 2022 | Estimated PPV uptake (%) | Estimated PPV coverage (%) |
|---|---|---|---|
| 65 years | 68483 | 13.5 | 31.1 |
| 66 years | 65,668 | 11.3 | 44.1 |
| 67 years | 64,530 | 7.6 | 51.1 |
| 68 years | 65,703 | 6.2 | 55.9 |
| 69 years | 63,455 | 5.3 | 59.6 |
| 70 to 74 years | 326,544 | 4.7 | 71.4 |
| 75 years and over | 630,232 | 2.0 | 83.3 |
| Total | 1,284,615 | 4.4 | 71.3 |
Coverage among individuals aged 2 to 64 years in clinical risk groups
Vaccine coverage estimates among individuals aged 2 to 64 years in clinical risk groups ranged from 39.5 % (chronic liver disease) to 70.5 % (cochlear implants) (Table 3). Coverage among individuals with Asplenia or dysfunction of the spleen was estimated at 45.9 %, which was 6.8 percentage points higher than in 2020 to 2021. Coverage estimates for most of the remaining clinical risk groups were higher than last year’s estimates (range: 0.8 percentage points (coronary heart disease) to 2.1 percentage points (cerebrospinal fluid leaks)), except among individuals with cochlear implants, for whom coverage was 0.2 percentage points lower than last year (data not shown).
Table 3. Vaccine coverage by individual clinical risk group as of 31 March 2022 in England
| Clinical risk group | GP-registered individuals on 31 March 2022 | Estimated PPV coverage (%) |
|---|---|---|
| Asplenia / dysfunction of the spleen | 287,769 | 45.9 |
| Chronic respiratory disease | 501,745 | 56.8 |
| Chronic heart disease | 830,699 | 44.1 |
| Chronic kidney disease | 86,502 | 54.6 |
| Chronic liver disease | 125,149 | 39.5 |
| Diabetes requiring insulin or oral hypoglycaemic medication | 1,503,772 | 56.2 |
| Immuno-suppression | 1,061,209 | 40.5 |
| Cochlear implants | 9,215 | 70.5 |
| Cerebrospinal fluid leaks | 5,391 | 41.0 |
Uptake estimates are not presented for individual clinical risk groups due to data quality issues. The following section will present PPV uptake among individuals included in one or more risk groups.
Coverage and uptake among individuals aged 65 years and over, and individuals aged 2 to 64 years in clinical risk groups, by gender
Estimates of vaccine coverage and uptake were separated by gender in the group of individuals aged 65 years and over and the group of individuals aged 2 to 64 years in one or more clinical risk groups. It should be noted that in contrast to the clinical risk group separated analysis above, in which patients were counted in each clinical risk group they were identified in, the gender-separated analysis counted patients in one or more risk groups only once. Due to small numbers, estimates were suppressed for 67 people, for whom gender was unknown or unspecified.
Coverage estimates for women (71.8 %) and men (71.1 %) were considerably higher among individuals aged 65 years and over than among individuals in one or more clinical risk groups (women 46.4 %, men 46.0 %) (Table 4).
Coverage estimates among individuals aged 65 years and were 1.0 percentage point higher among women and 0.8 percentage points higher among men than in 2020 to 2021 (data not shown).
Table 4. Vaccine coverage and uptake among GP-registered individuals aged 65 years and over, and GP-registered individuals aged 2 to 64 years in one or more clinical risk groups, as of 31 March 2022, by gender in England
Individuals aged 65 years and over
| Gender | GP-registered individuals on 31 March 2022 (n) | Estimated PPV uptake (%) | Estimated PPV coverage (%) |
|---|---|---|---|
| Men | 4,849,328 | 5.0 | 71.1 |
| Women | 5,663,174 | 4.6 | 71.8 |
| Total | 10,512,502 | 4.8 | 71.5 |
Individuals in one or more clinical risk groups
| Gender | GP-registered individuals on 31 March 2022 (n) | Estimated PPV uptake (%) | Estimated PPV coverage (%) |
|---|---|---|---|
| Men | 2,058,935 | 5.4 | 46.0 |
| Women | 1,811,899 | 5.5 | 46.4 |
| Total | 3,870,834 | 5.5 | 46.2 |
Among individuals aged 65 years and over, uptake estimates were 4.6 % among women and 5.0 % among men, which were 0.3 percentage points lower among women and 0.1 percentage points higher among men compared to 2020 to 2021.
Among individuals in one or more clinical risk groups, uptake estimates were 5.5 % among women and 5.4 % among men.
Coverage and uptake estimates for women and men in one or more clinical risk groups were not compared to estimates from 2020 to 2021 because of data quality issues in 2020 to 2021.
Discussion
The current analysis used GP-aggregated data from 6,242 GP practices in England. The response rate of GP practices was 97.7 % and was considered representative of the English population belonging to the groups of individuals assessed in the current report.
We observed a 0.9 percentage point increase in estimated coverage since last year to 71.5 % and a 0.1 percentage point decrease in estimated uptake to 4.8 %. The trends of increasing coverage and decreasing uptake across patient groups of increasing age were consistent with the previous year.
The observed patterns of increasing coverage and decreasing uptake across age groups are expected. The number of people, who received PPV in the past 12 months as a proportion of the population in the age group (uptake) is expected to decrease with increasing age because older individuals, who have been eligible for longer, are more likely to have had the vaccine prior to the most recent 12 months (contributing to coverage statistics). The increase in vaccine coverage in the older age groups demonstrates that PPV continues to be offered opportunistically in primary care to individuals aged 65 years and over who remain eligible as they age.
Although the pattern of increasing coverage and decreasing uptake across age groups persisted in analyses that were separated by 7 NHS commissioning regions, varying coverage and uptake estimates across regions suggest that efforts to promote PPV should be sustained across all geographies.
In response to the COVID-19 pandemic, nationwide social distancing measures were initiated from 23 March 2020 and specific guidance for elderly and clinical risk groups to temporarily shield have been in place throughout the pandemic (7), potentially disrupting the delivery of PPV vaccination programme. Nonetheless, vaccine coverage and uptake among individuals aged 65 years and over appear to have increased since 2019 to 2020 (2). This may be due to increased awareness of the importance of vaccination amongst people in this age group due to their prioritisation in the COVID-19 vaccination campaign, as well as increased awareness among healthcare professionals.
Prioritisation of the elderly population and most of the clinical risk groups included in this report during the COVID-19 vaccination campaign roll-out might further positively have influenced the number of PPV vaccines offered and accepted among the reported population groups in GP practices in England.
A review of the methodology used to define clinical risk groups was performed in 2018 and implemented for PPV data extraction for the first time in 2020 to 2021. The new data specifications for extracting data among individuals in clinical risk groups favoured specificity over sensitivity to improve confidence that individuals, who were identified in a clinical risk group were genuinely eligible for PPV.
Vaccine coverage among women (46.4 %) and men (46.0 %) aged 2 to 64 years in one or more clinical risk groups were considerably lower overall and by most individual clinical risk groups (range: 39.5 % (chronic liver disease) to 56.8 % (chronic respiratory disease)), than coverage among women (71.8 %) and men (71.1 %) aged 65 years and more, except among individuals with cochlear implants (70.5 %). The differences in coverage among individuals in clinical risk groups could suggest that vaccine offers or awareness of eligibility and importance of PPV among individuals and clinicians vary substantially according to clinical risk.
References
1. UKHSA (2020). The Green Book, chapter 25: Pneumococcal
2. UKHSA (2021). Prenatal pertussis vaccination coverage in England from October to December 2022.
3. Ladhani SN, Collins S, Djennad A, Sheppard CL, Borrow R (2018). Rapid increase in non-vaccine serotypes causing invasive pneumococcal disease in England and Wales, 2000 to 2017: a prospective national observational cohort study. Lancet Infectious Diseases: volume 18 number 4, pages 441 to 451
4. PHE (2014). Pneumococcal Polysaccharide Vaccine (PPV) Uptake.
5. Department of Health and Chief Medical Officer (2003). Adult immunisation update. PLO CMO (2003)6
6. Djennad A, Ramsay ME, Pebody R and others (2018). ‘Effectiveness of 23-valent Polysaccharide Pneumococcal Vaccine and changes in invasive pneumococcal disease incidence from 2000 to 2017 in those aged 65 and over in England and Wales’. EClinincalMedicine volume 6, pages 42 to 50.
7. UKHSA (2021, updated 2023). COVID-19: guidance for people whose immune system means they are at higher risk