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COVID-19 vaccine waning and effectiveness and side-effects of boosters: a prospective community study from the ZOE COVID Study [1]

['Cristina Menni', 'Cristina.Menni Kcl.A.Uk', 'Department Of Twin Research', 'Genetic Epidemiology', "King'S College London", 'London', 'Anna May', 'Zoe Limited', 'Lorenzo Polidori', 'Panayiotis Louca']

Date: 2022-08

After 5 months, vaccine effectiveness remained high among individuals younger than 55 years. Booster doses restore vaccine effectiveness. Adverse reactions after booster doses were similar to those after the second dose. Homologous booster schedules had fewer reported systemic side-effects than heterologous boosters.

We included 620 793 participants who received two vaccine doses (204 731 [33·0%] received BNT162b2, 405 239 [65·3%] received ChAdOx1 nCoV-19, and 10 823 [1·7%] received mRNA-1273) and subsequently had a SARS-CoV-2 test result between May 23 (chosen to exclude the period of alpha [B.1.1.7] variant dominance) and Nov 23, 2021. 62 172 (10·0%) vaccinated individuals tested positive for SARS-CoV-2 and were compared with 40 345 unvaccinated controls (6726 [16·7%] of whom tested positive). Vaccine effectiveness waned after the second dose: at 5 months, BNT162b2 effectiveness was 82·1% (95% CI 81·3–82·9), ChAdOx1 nCoV-19 effectiveness was 75·7% (74·9–76·4), and mRNA-1273 effectiveness was 84·3% (81·2–86·9). Vaccine effectiveness decreased more among individuals aged 55 years or older and among those with comorbidities. 135 932 individuals aged 55 years or older received a booster (2123 [1·6%] of whom tested positive). Vaccine effectiveness for booster doses in 0–3 months after BNT162b2 primary vaccination was higher than 92·5%, and effectiveness for heterologous boosters after ChAdOx1 nCoV-19 was at least 88·8%. For the booster reactogenicity analysis, in 317 011 participants, the most common systemic symptom was fatigue (in 31 881 [10·1%] participants) and the most common local symptom was tenderness (in 187 767 [59·2%]). Systemic side-effects were more common for heterologous schedules (32 632 [17·9%] of 182 374) than for homologous schedules (17 707 [13·2%] of 134 637; odds ratio 1·5, 95% CI 1·5–1·6, p<0·0001).

We used SARS-CoV-2 positivity rates in individuals from a longitudinal, prospective, community-based study (ZOE COVID Study), in which data were self-reported through an app, to assess the effectiveness of three COVID-19 vaccines (ChAdOx1 nCov19 [Oxford-AstraZeneca], BNT162b2 [Pfizer-BioNtech], and mRNA1273 [Moderna]) against infection in the 8 months after completion of primary vaccination series. In individuals receiving boosters, we investigated vaccine effectiveness and reactogenicity, by assessing 16 self-reported systemic and localised side-effects. We used multivariate Poisson regression models adjusting for confounders to estimate vaccine effectiveness.

With the surge of new SARS-CoV-2 variants, countries have begun offering COVID-19 vaccine booster doses to high-risk groups and, more recently, to the adult population in general. However, uncertainty remains over how long primary vaccination series remain effective, the ideal timing for booster doses, and the safety of heterologous booster regimens. We aimed to investigate COVID-19 primary vaccine series effectiveness and its waning, and the safety and effectiveness of booster doses, in a UK community setting.

Here, we aimed to investigate vaccine effectiveness (of ChAdOx1 nCov19, BNT162b2, and mRNA1273) against infection in the 8 months following primary vaccination in a large prospective longitudinal community study of app users undergoing regular and ad-hoc SARS-CoV-2 testing. We further investigated the improved effectiveness and reactogenicity of a booster dose in a subset of individuals who had received one by Nov 23, 2021.

The COV-BOOST multicentre, phase 2 randomised controlled trial in the UK (n=2878) found that booster schedules increased both neutralising antibodies and cellular responses within 28 days of administration.No safety concerns were raised, and side-effect profiles were similar to those seen with primary vaccination. As booster doses are offered to increasingly younger and less at-risk groups, assessing the number of months up to which vaccination is effective, and thus determining the ideal timing for boosters, becomes crucial for public health policy and resource optimisation. Moreover, issues regarding the safety of mix-and-match boosters are of considerable public concern, hence the need to compare systemic and localised side-effects for heterologous versus homologous boosters.

Safety and immunogenicity of seven COVID-19 vaccines as a third dose (booster) following two doses of ChAdOx1 nCov-19 or BNT162b2 in the UK (COV-BOOST): a blinded, multicentre, randomised, controlled, phase 2 trial.

The effectiveness against infection of COVID-19 vaccines waned considerably 5–8 months after primary vaccination, although it remained high, particularly among people younger than 55 years. Vaccine boosters were effective in restoring protection against infection and had a good safety profile in the community. The safety profile was better for homologous booster schedules than for heterologous ones.

We report that both for mRNA (mRNA-1273 [Moderna] and BNT162b2) and viral vector (ChAdOx1 nCov-19) COVID-19 vaccines, effectiveness against infection substantially decreased over 5–8 months compared with 1 month after the second dose. Vaccine waning was lower among the younger age group (<55 years), with effectiveness above 76·7% 5 months after the second dose. We report no differences in effectiveness between months 5 and 6 for any of the vaccines. We also found that a booster dose at 6 months restored vaccine effectiveness to higher levels than those seen 1 month after the second dose. Systemic side-effects after booster vaccination were minor and affected 50 339 (15·9%) of 317 011 individuals, but post-vaccine systemic reactogenicity was higher in those receiving a heterologous booster schedule than in those receiving a homologous booster.

There is a gap in knowledge regarding the actual waning in vaccine effectiveness against infection of both viral vector and mRNA COVID-19 vaccines after 5 months by demographic groups, and the restoration of effectiveness by boosters, particularly that of heterologous booster schedules, along with the side-effect profiles for homologous and heterologous boosters in the community.

We searched PubMed for articles published up to Dec 20, 2021, using the terms “vaccine effectiveness waning” or “vaccine booster” and “COVID-19”. We found reviews summarising that titres of binding and neutralising antibodies wane over time for all vaccines and that this is also applicable to COVID-19 vaccines. For SARS-CoV-2, a preprint suggested that vaccine effectiveness was 44·1% for ChAdOx1 nCoV-19 (Oxford-AstraZeneca) and 62·5% for BNT162b2 (Pfizer-BioNtech) at least 20 weeks after receiving the second dose. Similar results have been reported in Qatar, but effectiveness against hospitalisation and death remained high after 6 months. Risk of infection has also been shown to increase considerably 6 months after vaccination in a large study in US veterans, with the increase in risk being much lower for mRNA-based vaccines than for Ad.26.COV2.S (Janssen), a viral vector-based vaccine. Two Israeli studies reported that a booster dose after vaccination with BNT162b2 could raise protection against symptomatic infection up to 93·1%. The COV-BOOST randomised controlled trial found that booster schedules increased both humoral and cellular responses to SARS-CoV-2, and that the side-effects were similar to those seen with primary vaccination.

A systematic review of 39 studies showed vaccine effectiveness against symptomatic SARS-CoV-2 infection in the general population to be 89–97% for BNT162b2, 92% for ChAdOx1 nCoV-19 (Oxford-AstraZeneca), and 94% for mRNA-1273.However, vaccine effectiveness has been reported to drop to 44·1% with ChAdOx1 nCoV-19 or to 62·5% with BNT162b2 by week 20 after the second dose.Risk of infection also increased considerably 6 months after vaccination in data from the National Israeli databaseand in a study of 780 225 individuals in the USA, with the increased risk being lower for mRNA vaccines (BNT162b2 and mRNA-123) than for Ad.26.COV2.S (Janssen), a viral vector vaccine.With the addition of novel COVID-19 variants of concern,several countries have offered COVID-19 vaccine boosters to the highest-risk groups to mitigate the pandemic.A booster dose of the BNT162b2 vaccine reduced the rates of both infection and severe COVID-19 illness in the Israeli population older than 60 yearsand overall.Boosters of mRNA-based vaccines were also safe and effective in randomised controlled trials,with good immunogenicity observed for both homologous and heterologous booster doses.After receiving a booster dose, protection against symptomatic infection increased to over 93·1%,resulting in a proposed regimen of universal boosters 6 months after the second dose.

Safety and immunogenicity of seven COVID-19 vaccines as a third dose (booster) following two doses of ChAdOx1 nCov-19 or BNT162b2 in the UK (COV-BOOST): a blinded, multicentre, randomised, controlled, phase 2 trial.

Safety and immunogenicity of seven COVID-19 vaccines as a third dose (booster) following two doses of ChAdOx1 nCov-19 or BNT162b2 in the UK (COV-BOOST): a blinded, multicentre, randomised, controlled, phase 2 trial.

Effectiveness of a third dose of the BNT162b2 mRNA COVID-19 vaccine for preventing severe outcomes in Israel: an observational study.

The two-dose COVID-19 vaccination campaign substantially reduced hospitalisations and deaths despite high infection rates.However, the effectiveness against infection, as happens also for other vaccines, wanes within months of the second dose.Studies in Qatar showed substantial waningin effectiveness against SARS-CoV-2 infection from month 4 after the second dose for BNT162b2 (tozinameran; Pfizer-BioNtech),although effectiveness against severe disease, hospitalisation, and death remained high 6 months after vaccination for both BNT162b2 and mRNA-1273 (elasomeran; Moderna).

Associations of BNT162b2 vaccination with SARS-CoV-2 infection and hospital admission and death with COVID-19 in nursing homes and healthcare workers in Catalonia: prospective cohort study.

Effectiveness of the Pfizer-BioNTech and Oxford-AstraZeneca vaccines on COVID-19 related symptoms, hospital admissions, and mortality in older adults in England: test negative case-control study.

ZOE developed the app for data collection as a not-for-profit endeavour. ZOE received a grant from the UK Department of Health and Social Care to provide ongoing surveillance data. Employees of the funder were involved in most aspects of the study.

To investigate systemic and local adverse effects in individuals after receiving a booster, we computed the percentage of users reporting side-effects in the 8 days following the injection. We also considered the symptomatology of the same people in the 8 days following their second dose to compare reactogenicity of third doses with that of second doses. We compared the reactogenicity of different vaccines using Pearl's adjustment ( appendix p 3 ).

We investigated the effectiveness of vaccine boosters in preventing infection in a subset of app users who received two primary doses of BNT162b2 or ChAdOx1 nCoV-19, received either a BNT162b2 or an mRNA-1273 booster dose between Sept 16 and Nov 22, 2021, and were aged 55 years or older. As a control group, we selected individuals aged 55 years or older who received two primary doses of BNT162b2 or ChAdOx1 nCoV-19 but had not yet taken up their booster dose. We used adjusted Poisson regressions to compare the positivity rates in individuals with booster doses versus those with only two doses. We obtained the estimate of the log difference in the positivity rates of individuals who received a booster and control individuals who received two vaccine doses from the Poisson regression model. We combined the estimated difference between these two groups to the estimated risk reduction compared with unvaccinated individuals (measured at 0–3 months post-vaccination; more details in appendix p 3 ).

Additionally, we tested the role of covariates in risk of infection post-vaccination by running stratified Poisson models (adjusted for confounders) on categories of age and comorbidities ( appendix p 2 ). We then did sensitivity analyses in individuals who test frequently (ie, health-care workers), those who were previously infected, and those with symptomatic infection to ensure these were not a source of bias. We further assessed whether loss to follow-up was a source of bias, by comparing the baseline characteristics of individuals who stayed enrolled in the study and reported testing results several months post-vaccination with those of individuals who were lost to follow-up. We further investigated vaccine effectiveness against hospitalisation by running the same model, with hospitalisation as the endpoint.

In participants vaccinated with two doses of BNT162b2, ChAdOx1 nCoV-19, or mRNA-1273 who were subsequently tested for SARS-CoV-2 infection, we investigated changes in infection rates in the 8 months after the second dose, compared with those of unvaccinated app users.After adjusting for age (<55 years and ≥55 years), sex, previous infection (binary variable), health-care worker status (binary variable), comorbidities (binary variable, with or without comorbidities), number of tests, and weekly incidence per million individuals in the UK at the time of the infection to control for background positivity level as previously described,we defined vaccine effectiveness, VE, as the following: VE = 1 – RRwhere the risk ratio RR is the exponential of the treatment coefficient in the Poisson regression model, iε[BNT162b1, ChAdOx1 nCoV-19, mRNA-1273] and nε[1, 2, 3, 4, 5, 6, 7, 8]. Test results of individuals who received a booster were excluded after their booster date.

Vaccine side-effects and SARS-CoV-2 infection after vaccination in users of the COVID Symptom Study app in the UK: a prospective observational study.

Vaccine side-effects and SARS-CoV-2 infection after vaccination in users of the COVID Symptom Study app in the UK: a prospective observational study.

As a sub-analysis, we also investigated illness severity, defined as having two of three respiratory symptoms (chest pain, persistent cough, and shortness of breath),and hospital admission in individuals testing positive for SARS-CoV-2 5–6 months after receiving both primary doses of the available vaccines.

Our primary outcome was infection rates (eg, self-reported lateral flow or PCR test positivity) in individuals 5–8 months after receiving both primary doses of the available vaccines and after receiving a booster shot with either BNT162b2 or mRNA-1273. Our secondary outcome was self-reported reactogenicity within 8 days of the booster dose.

Ethical approval for use of the ZOE app for research purposes in the UK was obtained from King's College London Ethics Committee (review reference LRS-19/20–18210), and all users provided consent for non-commercial use.

Upon registration to the ZOE app, participants provide consent for their data to be used in COVID-19 research. They self-report demographic characteristics including age, sex, body-mass index (BMI), smoking, race or ethnicity, health-care worker status, and comorbidity data ( appendix p 2 ). Participants are prompted to report any symptoms, SARS-CoV-2 tests and results, vaccination and booster details, and health-care access daily through app notifications.Individuals without symptoms are similarly encouraged to report through the app daily. Participants were asked if they had been vaccinated for COVID-19 and if so, to record the type of vaccine and date of administration. For 8 days from each vaccination day, users were asked daily whether they had any systemic or local side-effects, as previously described.Test positivity (regular or ad hoc) was self-reported through the app. The ZOE COVID Study app sends invites for testing to people reporting symptoms (including symptoms not recognised at a given timepoint by the UK Government as indicative of SARS-CoV-2 infection). When people reported more than one PCR or lateral flow result after vaccination, we selected the first test if positive or the latest test if all were negative.

Vaccine side-effects and SARS-CoV-2 infection after vaccination in users of the COVID Symptom Study app in the UK: a prospective observational study.

Vaccine side-effects and SARS-CoV-2 infection after vaccination in users of the COVID Symptom Study app in the UK: a prospective observational study.

This prospective cohort study analysed data acquired from UK voluntary participants in the ZOE COVID Study,who self-reported data through an app ( appendix p 2 ). We analysed data collected from May 23, 2021, (to exclude the period of alpha [B.1.1.7] variant dominance) to Nov 23, 2021, when there was a data freeze. A consort diagram with the study design is presented in the appendix (p 6) . Additional details for data sources, analyses, and selection of covariates are also provided in the appendix (pp 2–5 ).

Results

2, SD 5·33). On average, fully vaccinated individuals completed their second dose 3·84 months (IQR 3–5) before the analysis. Table Descriptive characteristics of the study population, by type of vaccine used in the primary immunisation series BNT162b2 (n=204 731) ChAdOx1 nCoV-19 (n=405 239) mRNA-1273 (n=10 823) Unvaccinated (n=40 345) Sex Female 134 032 (65·5%) 242 829 (59·9%) 6235 (57·6%) 25 969 (64·4%) Male 70 699 (34·5%) 162 410 (40·1%) 4588 (42·4%) 14 376 (35·6%) Age, years 50·0 (13·9);52 (38–62) 54·8 (9·9);56 (48–63) 39·1 (8·3);39 (33–46) 37·7 (13·2);34 (27–47) BMI, kg/m2 26·6 (5·6) 26·8 (5·3) 25·2 (4·6) 25·4 (5·3) Health-care workers 27 110 (13·2%) 9522 (2·3%) 84 (0·7%) 1794 (4·4%) Comorbidities 41 136 (20·1%) 66 471 (16·4%) 755 (7·0%) 3958 (9·8%) Infection post-vaccination 16 037 (7·8%) 45 384 (11·2%) 751 (6·9%) 6726 (16·7%) * Infections during the study period. PCR confirmed 11 491 (71·7%) 32 082 (70·7%) 525 (69·9%) 4868 (72·4%) * Infections during the study period. LFT confirmed 4546 (28·3%) 13 302 (29·3%) 226 (30·1%) 1858 (27·6%) * Infections during the study period. Infections with symptom assessment 15 320 (7·5%) 43 706 (10·8%) 739 (6·8%) 4962 (12·3%) Symptomatic infections post-vaccination 13 682 (6·7%) 40 354 (10·0%) 646 (6·0%) 4575 (11·3%) * Infections during the study period. Booster 98 008 (47·9%) † Data indicate that of 204 731 individuals who received two doses of BNT162b2 in the primary immunisation series, 98 008 received a booster dose, including 91 692 who received BNT162b2 and 6316 who received mRNA-1273. 120 525 (29·7%) ‡ Data indicate that of 405 239 individuals who received two doses of ChAdOx1 nCoV-19 in the primary immunisation series, 120 525 received a booster dose, including 102 780 who received BNT162b2 and 17 745 who received mRNA-1273. 0 0 Data are n, n (%), mean (SD), or mean (SD); median (IQR). BMI=body-mass index. LFT=lateral flow test. For the analysis of vaccine effectiveness of two doses, we included 620 793 UK app users who reported being fully vaccinated and subsequently tested for SARS-CoV-2 with an RT-PCR-based test or a lateral flow test between May 23 (once the SARS-CoV-2 delta [B.1.617.2] variant became predominant) and Nov 23, 2021, and 40 345 unvaccinated users who had a PCR or lateral flow test result in the same period ( appendix p 6 ). 204 731 (33·0%) individuals received two doses of BNT162b2, 405 239 (65·3%) received two doses of ChAdOx1 nCoV-19, and 10 823 (1·7%) received two doses of mRNA-1273 (demographic characteristics are shown in the table ). The study sample was predominantly female (409 065 [61·9%] of 661 138) and 137 939 (20·1%) were obese (mean BMI 26·61 kg/m, SD 5·33). On average, fully vaccinated individuals completed their second dose 3·84 months (IQR 3–5) before the analysis.

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et al. Vaccine side-effects and SARS-CoV-2 infection after vaccination in users of the COVID Symptom Study app in the UK: a prospective observational study. 25 Hayat MJ

Higgins M Understanding Poisson regression. figure 1, Figure 1 Primary immunisation series effectiveness against infection over time, overall (A) and by age (B) and presence of comorbidities (C) Show full caption wThe graphs represent the risk reduction for infection of the vaccinated group compared with the unvaccinated group by vaccine type and months since vaccination. Dotted lines indicate 95% CIs. We investigated changes in infection rates after completing the second dose. After the second dose, 62 172 (10·0%) of 620 793 vaccinated individuals and 6726 (16·7%) of 40 345 unvaccinated controls tested positive for SARS-CoV-2 infection. Data were available for up to 8 months after the second dose for BNT162b2, for up to 6 months for ChAdOx1 nCoV-19, and for up to 5 months for mRNA-1273. In line with our previous reports,we observed that 1 month after the second dose, infection risk in the vaccinated group was significantly lower than in the unvaccinated population (vaccine effectiveness of 91·6%, 95% CI 90·7–92·4, for BNT162b2; 83·1%, 82·2–84·0, for ChAdOx1 nCoV-19; and 94·1%, 92·3–95·5, for mRNA-1273), after adjusting for confounders using Poisson regressions appendix pp 7–8 ). As depicted in figure 1A , vaccine effectiveness gradually started waning after the second shot. BNT162b2 effectiveness was 82·1% (81·3–82·9) at 5 months, 81·6% (80·8–82·4) at 6 months, and 75·7% (73·4–77·7) at 8 months; ChAdOx1 nCoV-19 effectiveness was 75·7% (74·9–76·4) at 5 months and 75·2% (74·3–76·1) at 6 months; and mRNA-1273 effectiveness was 84·3% (81·2–86·9) at 5 months ( appendix pp 7–8 ).

For each vaccine, we observed a larger waning of effectiveness in individuals aged 55 years or older than in those younger than 55 years, with similar trends observed over time ( figure 1B ). For this analysis, we included 300 944 participants who were doubly vaccinated and younger than 55 years, of whom 41 137 (13·7%) tested positive for SARS-CoV-2, and 319 849 aged 55 years or older, of whom 21 035 (6·6%) tested positive. The control group consisted of unvaccinated participants: 34 355 younger than 55 years, of whom 5992 (17·4%) tested positive, and 5990 aged 55 years or older, of whom 734 (12·3%) tested positive.

At 5 months, BNT162b2 vaccine effectiveness was 76·3% (74·0–78·5) in those aged 55 years or older compared with 83·0% (82·0–83·8) in those younger than 55 years; at the same timepoint, ChAdOx1 nCoV-19 effectiveness was 67·8% (65·1–70·2) in those aged 55 years or older compared with 76·7% (75·9–77·6) in those younger than 55 years.

We found that individuals with comorbidities who received the BNT162b2 or ChAdOx1 nCoV-19 vaccine had lower vaccine effectiveness than individuals without comorbidities (eg, 77·5%, 74·9–79·9, vs 82·8%, 81·9–83·6, at 5 months with BNT162b2; and 70·8%, 68·0–73·5, vs 76·1%, 75·3–76·9, at 5 months with ChAdOx1 nCoV-19; figure 1C ). For this analysis, 512 431 participants without comorbidities who were doubly vaccinated (52 058 [10·2%] tested positive) were compared with 36 387 unvaccinated individuals with no comorbidities (6106 [16·8%] tested positive); and 108 362 individuals with at least one comorbidity who were doubly vaccinated (10 114 [9·3%] tested positive) were compared with 3958 unvaccinated individuals with at least one comorbidity (620 [15·7%] tested positive). Because the mRNA-1273 vaccine was offered to younger individuals without comorbidities, we could not do analyses stratified by age or comorbidities.

We did sensitivity analyses in participants who test frequently (ie, health-care workers), those who were previously infected, and those with symptomatic infection; we found that vaccine effectiveness at 5 months was not substantially different in any of these subgroups compared with the main analysis ( appendix p 9 ). To assess whether loss to follow-up was a source of bias, we compared the characteristics at baseline of individuals who stayed enrolled in the study and reported testing results several months post-vaccination with those of individuals who were lost to follow-up; we found that these groups were broadly similar ( table appendix p 10 ).

Vaccine effectiveness against severe infection and hospitalisation remained high 5–6 months after completion of the primary vaccination series (effectiveness against severe infection of 78·8%, 95% CI 77·1–80·3, and against hospitalisation of 84·1%, 81·0–86·7; appendix p 11 ). Moreover, vaccine effectiveness was higher among individuals younger than 55 years (effectiveness against severe infection of 79·2%, 77·4–80·8, and against hospitalisation of 84·3%, 80·7–87·2) than among individuals aged 55 years and older (effectiveness against severe infection of 66·5%, 57·5–73·5, and against hospitalisation of 80·4%, 70·7–86·9; appendix p 12 ). As the mRNA-1273 vaccine was offered to the younger age group with less severe infection outcomes, we could not do an analysis of effectiveness against severe illness or hospitalisation separately for this vaccine. For BNT162b2 and ChAdOx1 nCoV-19, vaccine effectiveness estimates were greater in younger than in older individuals ( appendix p 12 ).

Figure 2 Effectiveness against infection of homologous and heterologous booster doses in individuals aged 55 years or older Show full caption Error bars indicate 95% CI. Vaccine effectiveness estimates for booster doses (or two doses) in 0–3 months after immunisation compared with no vaccination are shown. During the study period, 194 472 app users registered receiving booster shots with BNT162b2 and 24 061 with mRNA-1273. We assessed the effectiveness of homologous and heterologous booster doses in 135 932 participants aged 55 years or older who received a booster dose (2123 [1·6%] subsequently infected). For individuals who received a booster, we saw significant increases in effectiveness against infection in 0–3 months post-booster compared with the same time period after the second dose in 33 466 individuals aged 55 years or older doubly vaccinated without a booster (824 [2·5%] subsequently infected; appendix p 13 ). This translated to a vaccine effectiveness versus unvaccinated individuals aged 55 years or older of 95·3% (92·3–97·1) for homologous BNT162b2 schedules (n=63 632), 91·0% (89·2–92·5) for those receiving a BNT162b2 booster after two primary ChAdOx1 nCoV-19 doses (n=63 922), 88·8% (84·4–92·0) for those receiving an mRNA-1273 booster after two primary ChAdOx1 nCoV-19 doses (n=6000), and 92·5% (86·0–96·0) for those receiving an mRNA-1273 booster after two primary doses of BNT162b2 (n=2378; figure 2 appendix p 13 ).

2 (5·1). We further investigated the occurrence of systemic and local adverse effects within 8 days after administration of the booster dose. 317 011 participants completed at least one daily report of systemic and local side-effects after receiving the booster ( appendix pp 14–15 ). Of these, 27 761 (8·8%) received an mRNA-1273 third dose and 289 250 (91·2%) received BNT162b2; 134 637 (42·5%) participants received homologous prime–boost schedules and 182 374 (57·5%) received heterologous schedules. On average, the mean age of participants who received a booster was 65·4 years (SD 10·6) and the mean BMI was 26·5 kg/m(5·1).

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et al. Vaccine side-effects and SARS-CoV-2 infection after vaccination in users of the COVID Symptom Study app in the UK: a prospective observational study. Figure 3 Proportion of participants self-reporting adverse effects to the ZOE COVID Study app within 8 days after receiving a booster Show full caption Systemic and local side-effects after the booster are presented for homologous and heterologous dose combinations. After the booster, 50 339 (15·9%) of 317 011 individuals reported having at least one systemic adverse effect and 232 596 (73·4%) reported one or more local effects within 8 days of the injection. The most commonly reported systemic side-effects were fatigue and headache, and the most frequently reported local side-effects were tenderness and pain around the site of injection ( appendix p 14 ), the same as what was reported after the first two vaccine doses.For those receiving homologous BNT162b2 schedules, the proportion of participants who reported systemic side-effects after the booster was slightly lower than after the second dose (13·2%, 95% CI 13·0–13·3, for the third dose vs 19·2%, 19·0–19·4, for the second dose; odds ratio [OR] 1·6, 95% CI 1·5–1·6; p<0·0001) after adjusting for covariates ( figure 3 appendix p 16 ).

Individuals who received a heterologous booster dose had higher rates of systemic adverse effects (17·9%, 17·7–18·1; 32 632 of 182 374) than those who received a homologous booster dose (13·2%; 17 707 of 134 637; OR 1·5, 1·5–1·6, p<0·0001, vs homologous BNT162b2). Among those on a heterologous schedule, participants receiving a third mRNA-1273 dose after a second BNT162b2 or ChadOx nCoV-19 dose were more likely to report systemic side-effects (18·0%, 95% CI 17·1–18·8) than those receiving the other heterologous combination (16·1%, 15·9–16·2, for ChadOx1 nCoV-19 followed by BNT162b2; OR 1·2, 1·2–1·3, p<0·0001).

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[1] Url: https://www.thelancet.com/journals/laninf/article/PIIS1473-3099(22)00146-3/fulltext#

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