Waning Effectiveness of the BNT162b2 Vaccine Against Infection in Adolescents

Low Risk of SARS-CoV-2 Reinfection for Fully or Boosted mRNA Vaccinated Subjects in Sicily: A Population-Based Study Using Real-World Data

Background: Reinfections occur as a response to natural infections wanes and novel strains of SARS-CoV-2 emerge. The present research explored the correlation between sex, age, COVID-19 vaccination, prior infection hospitalization, and SARS-CoV-2 reinfection in Sicily, Italy. Materials and Methods: A population-based retrospective cohort study was articulated using the vaccination flux from a regional registry and the Sicilian COVID-19 monitoring system of the Italian Institute of Health. Only adult Sicilians were included in the study, and hazard ratios were calculated using Cox regression. Results: Partial vaccination provided some protection (adj-HR: 0.92), when compared to unvaccinated individuals; furthermore, reinfection risk was reduced by full vaccination (adj-HR: 0.43), and the booster dose (adj-HR: 0.41). Males had a lower risk than females of reinfection with SARS-CoV-2 (adj-HR: 0.75). Reinfection with SARS-CoV-2 was diminished by hospitalization during the first infection (adj-HR: 0.78). Reinfection risk was higher among those aged 30-39 and 40-49 compared to those aged 18-29, whereas those aged 60-69, 70-79, and 80+ were statistically protected. Reinfection was significantly more frequent during the wild-type-Alpha, Delta, Delta-Omicron, and Omicron dominance/codominance waves compared to the wild type. Conclusions: This study establishes a solid base for comprehending the reinfection phenomenon in Sicily by pinpointing the most urgent policy hurdles and identifying some of the major factors. COVID-19 vaccination, one of the most effective public health tools, protects against reinfection, mostly caused by the Omicron strain. Elderly and hospitalized people's lower risk suggests stricter PPE use.

Evaluation of Waning of SARS-CoV-2 Vaccine-Induced Immunity: A Systematic Review and Meta-analysis

Importance

Estimates of the rate of waning of vaccine effectiveness (VE) against COVID-19 are key to assess population levels of protection and future needs for booster doses to face the resurgence of epidemic waves.

Objective

To quantify the progressive waning of VE associated with the Delta and Omicron variants of SARS-CoV-2 by number of received doses.

Data Sources

PubMed and Web of Science were searched from the databases' inception to October 19, 2022, as well as reference lists of eligible articles. Preprints were included.

Study Selection

Selected studies for this systematic review and meta-analysis were original articles reporting estimates of VE over time against laboratory-confirmed SARS-CoV-2 infection and symptomatic disease.

Data Extraction and Synthesis

Estimates of VE at different time points from vaccination were retrieved from original studies. A secondary data analysis was performed to project VE at any time from last dose administration, improving the comparability across different studies and between the 2 considered variants. Pooled estimates were obtained from random-effects meta-analysis.

Main Outcomes and Measures

Outcomes were VE against laboratory-confirmed Omicron or Delta infection and symptomatic disease and half-life and waning rate associated with vaccine-induced protection.

Results

A total of 799 original articles and 149 reviews published in peer-reviewed journals and 35 preprints were identified. Of these, 40 studies were included in the analysis. Pooled estimates of VE of a primary vaccination cycle against laboratory-confirmed Omicron infection and symptomatic disease were both lower than 20% at 6 months from last dose administration. Booster doses restored VE to levels comparable to those acquired soon after the administration of the primary cycle. However, 9 months after booster administration, VE against Omicron was lower than 30% against laboratory-confirmed infection and symptomatic disease. The half-life of VE against symptomatic infection was estimated to be 87 days (95% CI, 67-129 days) for Omicron compared with 316 days (95% CI, 240-470 days) for Delta. Similar waning rates of VE were found for different age segments of the population.

Conclusions and Relevance

These findings suggest that the effectiveness of COVID-19 vaccines against laboratory-confirmed Omicron or Delta infection and symptomatic disease rapidly wanes over time after the primary vaccination cycle and booster dose. These results can inform the design of appropriate targets and timing for future vaccination programs.

Effectiveness of BNT162b2 vaccine against SARS-CoV-2 Delta and Omicron infection in adolescents, Norway, August 2021 to January 2022

OBJECTIVES

We estimated the BNT162b2 vaccine effectiveness (VE) against any (symptomatic or not) SARS-CoV-2 Delta and Omicron infection among adolescents (12-17-years-old) in Norway from August 2021 to January 2022.

METHODS

We used Cox proportional hazard models, where vaccine status was included as a time-varying covariate and models were adjusted for age, sex, comorbidities, residence county, birth country, and living conditions.

RESULTS

VE against Delta infection peaked at 68% (95%CI:64-71%) and 62% (95%CI:57-66%) in days 21-48 after the first dose among 12-15-year-olds and 16-17-year-olds respectively. Among 16-17-year-olds that received two doses, VE against Delta infection peaked at 93% (95%CI:90-95%) in days 35-62 and decreased to 84% (95%CI:76-89%) in ≥63 days after vaccination. We did not observe a protective effect against Omicron infection after receiving one dose. Among 16-17-year-olds, VE against Omicron infection peaked at 53% (95%CI:43-62%) in 7-34 days after the second dose and decreased to 23% (95%CI:3-40%) in ≥63 days after vaccination.

CONCLUSIONS

We found reduced protection after two BNT162b2 vaccine doses against any Omicron infection compared to Delta. Effectiveness decreased with time from vaccination for both variants. The impact of vaccination among adolescents on reducing infection and thus transmission is limited during Omicron dominance.

Enhanced virulence and waning vaccine-elicited antibodies account for breakthrough infections caused by SARS-CoV-2 delta and beyond

Here we interrogate the factors responsible for SARS-CoV-2 breakthrough infections in a K18-hACE2 transgenic mouse model. We show that Delta and the closely related Kappa variant cause viral pneumonia and severe lung lesions in K18-hACE2 mice. Human COVID-19 mRNA post-vaccination sera after the 2nd dose are significantly less efficient in neutralizing Delta/Kappa than early 614G virus in vitro and in vivo. By 5 months post-vaccination, ≥50% of donors lack detectable neutralizing antibodies against Delta and Kappa and all mice receiving 5-month post-vaccination sera die after the lethal challenges. Although a 3rd vaccine dose can boost antibody neutralization against Delta in vitro and in vivo, the mean log neutralization titers against the latest Omicron subvariants are 1/3-1/2 of those against the original 614D virus. Our results suggest that enhanced virulence, greater immune evasion, and waning of vaccine-elicited protection account for SARS-CoV-2 variants caused breakthrough infections.

Antibody and T cell responses against wild-type and Omicron SARS-CoV-2 after third-dose BNT162b2 in adolescents

The high effectiveness of the third dose of BNT162b2 in healthy adolescents against Omicron BA.1 has been reported in some studies, but immune responses conferring this protection are not yet elucidated. In this analysis, our study (NCT04800133) aims to evaluate the humoral and cellular responses against wild-type and Omicron (BA.1, BA.2 and/or BA.5) SARS-CoV-2 before and after a third dose of BNT162b2 in healthy adolescents. At 5 months after 2 doses, S IgG, S IgG Fc receptor-binding, and neutralising antibody responses waned significantly, yet neutralising antibodies remained detectable in all tested adolescents and S IgG avidity increased from 1 month after 2 doses. The antibody responses and S-specific IFN-γ⁺ and IL-2⁺ CD8⁺ T cell responses were significantly boosted in healthy adolescents after a homologous third dose of BNT162b2. Compared to adults, humoral responses for the third dose were non-inferior or superior in adolescents. The S-specific IFN-γ⁺ and IL-2⁺ CD4⁺ and CD8⁺ T cell responses in adolescents and adults were comparable or non-inferior. Interestingly, after 3 doses, adolescents had preserved S IgG, S IgG avidity, S IgG FcγRIIIa-binding, against Omicron BA.2, as well as preserved cellular responses against BA.1 S and moderate neutralisation levels against BA.1, BA.2 and BA.5. Sera from 100 and 96% of adolescents tested at 1 and 5 months after two doses could also neutralise BA.1. Our study found high antibody and T cell responses, including potent cross-variant reactivity, after three doses of BNT162b2 vaccine in adolescents in its current formulation, suggesting that current vaccines can be protective against symptomatic Omicron disease.

BNT162b2 COVID-19 vaccination uptake, safety, effectiveness and waning in children and young people aged 12-17 years in Scotland

Background

The two-dose BNT162b2 (Pfizer-BioNTech) vaccine has demonstrated high efficacy against COVID-19 disease in clinical trials of children and young people (CYP). Consequently, we investigated the uptake, safety, effectiveness and waning of the protective effect of the BNT162b2 against symptomatic COVID-19 in CYP aged 12-17 years in Scotland.

Methods

The analysis of the vaccine uptake was based on information from the Turas Vaccination Management Tool, inclusive of Mar 1, 2022. Vaccine safety was evaluated using national data on hospital admissions and General Practice (GP) consultations, through a self-controlled case series (SCCS) design, investigating 17 health outcomes of interest. Vaccine effectiveness (VE) against symptomatic COVID-19 disease for Delta and Omicron variants was estimated using a test-negative design (TND) and S-gene status in a prospective cohort study using the Scotland-wide Early Pandemic Evaluation and Enhanced Surveillance of COVID-19 (EAVE II) surveillance platform. The waning of the VE following each dose of BNT162b2 was assessed using a matching process followed by conditional logistic regression.

Findings

Between Aug 6, 2021 and Mar 1, 2022, 75.9% of the 112,609 CYP aged 16-17 years received the first and 49.0% the second COVID-19 vaccine dose. Among 237,681 CYP aged 12-15 years, the uptake was 64.5% and 37.2%, respectively. For 12-17-year-olds, BNT162b2 showed an excellent safety record, with no increase in hospital stays following vaccination for any of the 17 investigated health outcomes. In the 16-17-year-old group, VE against symptomatic COVID-19 during the Delta period was 64.2% (95% confidence interval [CI] 59.2-68.5) at 2-5 weeks after the first dose and 95.6% (77.0-99.1) at 2-5 weeks after the second dose. The respective VEs against symptomatic COVID-19 in the Omicron period were 22.8% (95% CI -6.4-44.0) and 65.5% (95% CI 56.0-73.0). In children aged 12-15 years, VE against symptomatic COVID-19 during the Delta period was 65.4% (95% CI 61.5-68.8) at 2-5 weeks after the first dose, with no observed cases at 2-5 weeks after the second dose. The corresponding VE against symptomatic COVID-19 during the Omicron period were 30.2% (95% CI 18.4-40.3) and 81.2% (95% CI 77.7-84.2). The waning of the protective effect against the symptomatic disease began after five weeks post-first and post-second dose.

Interpretation

During the study period, uptake of BNT162b2 in Scotland has covered more than two-thirds of CYP aged 12-17 years with the first dose and about 40% with the second dose. We found no increased likelihood of admission to hospital with a range of health outcomes in the period after vaccination. Vaccination with both doses was associated with a substantial reduction in the risk of COVID-19 symptomatic disease during both the Delta and Omicron periods, but this protection began to wane after five weeks.

Funding

UK Research and Innovation (Medical Research Council); Research and Innovation Industrial Strategy Challenge Fund; Chief Scientist's Office of the Scottish Government; Health Data Research UK; National Core Studies - Data and Connectivity.

Effectiveness Associated With BNT162b2 Vaccine Against Emergency Department and Urgent Care Encounters for Delta and Omicron SARS-CoV-2 Infection Among Adolescents Aged 12 to 17 Years

Importance

Data about the duration of protection of 2 and 3 doses of BNT162b2 in children and adolescents are needed to help inform recommendations for boosters in this age group.

Objective

To evaluate vaccine effectiveness (VE) and durability associated with 2 doses of BNT162b2 against Delta- and Omicron-related emergency department (ED) and urgent care (UC) encounters among adolescents aged 12 to 17 years and to estimate VE associated with 3 doses against these same outcomes.

Design, Setting, and Participants

This test-negative case-control study was conducted at Kaiser Permanente Southern California, an integrated health care system using electronic health records in the US. Participants included Kaiser Permanente Southern California members ages 12 to 17 years with an ED or UC encounter from November 1, 2021, through March 18, 2022, for acute respiratory infection who were tested for SARS-CoV-2 via a reverse transction-polymerase chain reaction test. Analyses were conducted from March 21 to June 22, 2022.

Exposures

BNT162b2 vaccination status ascertained from electronic health records and state registry data.

Main Outcomes and Measures

The main outcome was VE associated with BNT162b2 against ED and UC encounters related to Delta or Omicron variant SARS-CoV-2 infection.

Results

Analyses were conducted among 3168 adolescents, including 1004 with ED visits and 2164 with UC visits. Median (IQR) age was 15 (13-16) years, and 1461 (46.1%) were boys. In adjusted analyses, VE associated with 2 doses of BNT162b2 against ED or UC encounters was highest within the first 2 months for both Delta (89% [95% CI, 69% to 96%]) and Omicron (73% [95% CI, 54% to 84%]) variants but waned to 49% (95% CI, 27% to 65%) for the Delta variant and 16% (95% CI, -7% to 34%) for the Omicron variant at 6 months and beyond. A third dose of BNT162b2 was associated with improved protection against the Omicron variant (87% [95% CI, 72% to 94%]) after a median (IQR) of 19 (9-32) days after dose 3.

Conclusions and Relevance

These findings suggest that 2 doses of the BNT162b2 COVID-19 vaccine were associated with high levels of protection against ED and UC encounters related to the Delta and Omicron variants of SARS-CoV-2 in the first few months after vaccination. However, effectiveness waned over time, especially against Omicron. A third dose of BNT162b2 was associated with improved protection against Omicron beyond that seen initially after 2 doses, underscoring the importance of boosters for adolescents aged 12 to 17 years.

Pre-Omicron Vaccine Breakthrough Infection Induces Superior Cross-Neutralization against SARS-CoV-2 Omicron BA.1 Compared to Infection Alone

SARS-CoV-2 variants raise concern because of their high transmissibility and their ability to evade neutralizing antibodies elicited by prior infection or by vaccination. Here, we compared the neutralizing abilities of sera from 70 unvaccinated COVID-19 patients infected before the emergence of variants of concern (VOCs) and of 16 vaccine breakthrough infection (BTI) cases infected with Gamma or Delta against the ancestral B.1 strain, the Gamma, Delta and Omicron BA.1 VOCs using live virus. We further determined antibody levels against the Nucleocapsid (N) and full Spike proteins, the receptor-binding domain (RBD) and the N-terminal domain (NTD) of the Spike protein. Convalescent sera featured considerable variability in the neutralization of B.1 and in the cross-neutralization of different strains. Their neutralizing capacity moderately correlated with antibody levels against the Spike protein and the RBD. All but one convalescent serum failed to neutralize Omicron BA.1. Overall, convalescent sera from patients with moderate disease had higher antibody levels and displayed a higher neutralizing ability against all strains than patients with mild or severe forms of the disease. The sera from BTI cases fell into one of two categories: half the sera had a high neutralizing activity against the ancestral B.1 strain as well as against the infecting strain, while the other half had no or a very low neutralizing activity against all strains. Although antibody levels against the spike protein and the RBD were lower in BTI sera than in unvaccinated convalescent sera, most neutralizing sera also retained partial neutralizing activity against Omicron BA.1, suggestive of a better cross-neutralization and higher affinity of vaccine-elicited antibodies over virus-induced antibodies. Accordingly, the IC50: antibody level ratios were comparable for BTI and convalescent sera, but remained lower in the neutralizing convalescent sera from patients with moderate disease than in BTI sera. The neutralizing activity of BTI sera was strongly correlated with antibodies against the Spike protein and the RBD. Together, these findings highlight qualitative differences in antibody responses elicited by infection in vaccinated and unvaccinated individuals. They further indicate that breakthrough infection with a pre-Omicron variant boosts immunity and induces cross-neutralizing antibodies against different strains, including Omicron BA.1.

Effectiveness of heterologous and homologous covid-19 vaccine regimens: living systematic review with network meta-analysis

OBJECTIVE

To evaluate the effectiveness of heterologous and homologous covid-19 vaccine regimens with and without boosting in preventing covid-19 related infection, hospital admission, and death.

DESIGN

Living systematic review and network meta-analysis.

DATA SOURCES

World Health Organization covid-19 databases, including 38 sources of published studies and preprints.

STUDY SELECTION

Randomised controlled trials, cohort studies, and case-control studies.

METHODS

38 WHO covid-19 databases were searched on a weekly basis from 8 March 2022 to 31 July 2022. Studies that assessed the effectiveness of heterologous and homologous covid-19 vaccine regimens with or without a booster were identified. Studies were eligible when they reported the number of documented, symptomatic, severe covid-19 infections, covid-19 related hospital admissions, or covid-19 related deaths among populations that were vaccinated and unvaccinated. The primary measure was vaccine effectiveness calculated as 1−odds ratio. Secondary measures were surface under the cumulative ranking curve (SUCRA) scores and the relative effects for pairwise comparisons. The risk of bias was evaluated by using the risk of bias in non-randomised studies of interventions (ROBINS-I) tool for all cohort and case-control studies. The Cochrane risk of bias tool (version 2; ROB-2) was used to assess randomised controlled trials.

RESULTS

The second iteration of the analysis comprised 63 studies. 25 combinations of covid-19 vaccine regimens were identified, of which three doses of mRNA vaccine were found to be 93% (95% credible interval 70% to 98%) effective against asymptomatic or symptomatic covid-19 infections for non-delta or non-omicron related infections. Heterologous boosting using two dose adenovirus vector vaccines with one dose mRNA vaccine showed a vaccine effectiveness of 94% (72% to 99%) against non-delta or non-omicron related asymptomatic or symptomatic infections. Three doses of mRNA vaccine were found to be the most effective in reducing non-delta or non-omicron related hospital admission (96%, 82% to 99%). The vaccine effectiveness against death in people who received three doses of mRNA vaccine remains uncertain owing to confounders. The estimate for a four dose mRNA vaccine regimen was of low certainty, as only one study on the effectiveness of four doses could be included in this update. More evidence on four dose regimens will be needed to accurately assess the effectiveness of a fourth vaccine dose. For people with delta or omicron related infection, a two dose regimen of an adenovirus vector vaccine with one dose of mRNA booster was 77% (42% to 91%) effective against asymptomatic or symptomatic covid-19 infections, and a three dose regimen of a mRNA vaccine was 93% (76% to 98%) effective against covid-19 related hospital admission.

CONCLUSION

An mRNA booster is recommended to supplement any primary vaccine course. Heterologous and homologous three dose regimens work comparably well in preventing covid-19 infections, even against different variants. The effectiveness of three dose vaccine regimens against covid-19 related death remains uncertain.

SYSTEMATIC REVIEW REGISTRATION

This review was not registered. The protocol is included in the supplementary document.

READERS' NOTE

This article is a living systematic review that will be updated to reflect emerging evidence. Updates may occur for up to two years from the date of original publication. This version is update 1 of the original article published on 31 May 2022 (BMJ 2022;377:e069989), and previous versions can be found as data supplements (https://www.bmj.com/content/377/bmj-2022-069989/related). When citing this paper please consider adding the version number and date of access for clarity.

Short term, relative effectiveness of four doses versus three doses of BNT162b2 vaccine in people aged 60 years and older in Israel: retrospective, test negative, case-control study

OBJECTIVE

To examine the relative effectiveness of a fourth dose of the Pfizer-BioNTech mRNA (BNT162b2) vaccine compared with three vaccine doses over the span of 10 weeks.

DESIGN

Retrospective, test negative, case-control study, with a matched analysis and an unmatched multiple tests analysis.

SETTING

Nationally centralised database of Maccabi Healthcare Services, an Israeli national health fund for 2.5 million people; from 10 January 2022 (seven days after the fourth dose was first given to eligible individuals) to 13 March 2022, an omicron dominant period in Israel.

PARTICIPANTS

97 499 Maccabi Healthcare Services members aged 60 years and older, who were eligible to receive a fourth vaccine dose and obtained at least one polymerase chain reaction (PCR) test during the study.

MAIN OUTCOME MEASURES

Breakthrough SARS-CoV-2 infection, defined as a positive PCR test performed seven or more days after inoculation with the BNT162b2 vaccine; and breakthrough SARS-CoV-2 infection resulting in severe covid-19 disease, defined as hospital admission or death related to covid-19.

RESULTS

27 876 participants received the fourth BNT162b2 vaccine dose and 69 623 received three doses only. Of 106 participants who died during the follow-up period, 77 had had their third doses only and 23 had had their fourth doses during the first three weeks after inoculation. In the first three weeks, a fourth dose provided additional protection against both SARS-CoV-2 infection and severe disease relative to three doses of the vaccine. However, relative vaccine effectiveness against infection quickly decreased over time, peaking during the third week at 65.1% (95% confidence interval 63.0% to 67.1%) and falling to 22.0% (4.9% to 36.1%) by the end of the 10 week follow-up period. Unlike relative effectiveness against SARS-CoV-2 infection, the relative effectiveness of a fourth dose against severe covid-19 was maintained at a high level (>72%) throughout follow-up. However, severe disease was a relatively rare event, occurring in <1% of study participants who received four doses or three doses only.

CONCLUSIONS

A fourth dose of the BNT162b2 vaccine appears to have provided additional protection against both SARS-CoV-2 infection and severe covid-19 disease relative to three vaccine doses. However, relative effectiveness of the fourth dose against infection appears to wane sooner than that of the third dose.

Real-world effectiveness of BNT162b2 vaccine against SARS-CoV-2 infection among adolescents (12 to 17-year-olds) in Malaysia

OBJECTIVES

In this study, we aimed to investigate vaccine effectiveness (VE) against SARS-CoV-2 infections among adolescents aged 12 to 17 years in Malaysia and examine potential VE differences after full vaccination.

METHODS

We consolidated data on COVID-19 testing, vaccination, and outcomes for all public school-going adolescents in Malaysia from September 1, 2021, to December 31, 2021, and estimated the VE against SARS-CoV-2 infections during this period. Cases were defined as positive tests, either by reverse transcriptase- PCR (RT-PCR) or rapid antigen (RTK-Ag) testing, while controls were negative tests. Secondarily, we restricted the analysis to all tests performed in December 2021 and compared VE by month of full vaccination.

RESULTS

A total of 175,880 eligible tests (53.4% or 93,995 RT-PCR tests) were included. After full vaccination with BNT162b2, VE against SARS-CoV-2 infections was 65.7% (95% confidence interval [CI] 64.4, 66.9) over the study period. When restricted to tests in December 2021, VEs for those fully vaccinated in September 2021, October 2021, and November 2021 were comparable (60.6% [95% CI 23.7, 81.5], 56.9% [95% CI 51.1, 62.0], and 65.7% [95% CI 59.8, 70.7] respectively).

CONCLUSIONS

Among adolescents, full vaccination with BNT162b2 offered considerable protection against SARS-CoV-2 infections over at least three months without substantial evidence of waning.