Effectiveness of mRNA boosters after homologous primary series with BNT162b2 or ChAdOx1 against symptomatic infection and severe COVID-19 in Brazil and Scotland: A test-negative design case–control study

There is no author summary for this article yet. Authors can add summaries to their articles on ScienceOpen to make them more accessible to a non-specialist audience.

Abstract

Background

Brazil and Scotland have used mRNA boosters in their respective populations since September 2021, with Omicron’s emergence accelerating their booster program. Despite this, both countries have reported substantial recent increases in Coronavirus Disease 2019 (COVID-19) cases. The duration of the protection conferred by the booster dose against symptomatic Omicron cases and severe outcomes is unclear.

Methods and findings

Using a test-negative design, we analyzed national databases to estimate the vaccine effectiveness (VE) of a primary series (with ChAdOx1 or BNT162b2) plus an mRNA vaccine booster (with BNT162b2 or mRNA-1273) against symptomatic Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infection and severe COVID-19 outcomes (hospitalization or death) during the period of Omicron dominance in Brazil and Scotland compared to unvaccinated individuals. Additional analyses included stratification by age group (18 to 49, 50 to 64, ≥65). All individuals aged 18 years or older who reported acute respiratory illness symptoms and tested for SARS-CoV-2 infection between January 1, 2022, and April 23, 2022, in Brazil and Scotland were eligible for the study. At 14 to 29 days after the mRNA booster, the VE against symptomatic SARS-CoV-2 infection of ChAdOx1 plus BNT162b2 booster was 51.6%, (95% confidence interval (CI): [51.0, 52.2], p < 0.001) in Brazil and 67.1% (95% CI [65.5, 68.5], p < 0.001) in Scotland. At ≥4 months, protection against symptomatic infection waned to 4.2% (95% CI [0.7, 7.6], p = 0.02) in Brazil and 37.4% (95% CI [33.8, 40.9], p < 0.001) in Scotland. VE against severe outcomes in Brazil was 93.5% (95% CI [93.0, 94.0], p < 0.001) at 14 to 29 days post-booster, decreasing to 82.3% (95% CI [79.7, 84.7], p < 0.001) and 98.3% (95% CI [87.3, 99.8], p < 0.001) to 77.8% (95% CI [51.4, 89.9], p < 0.001) in Scotland for the same periods. Similar results were obtained with the primary series of BNT162b2 plus homologous booster. Potential limitations of this study were that we assumed that all cases included in the analysis were due to the Omicron variant based on the period of dominance and the limited follow-up time since the booster dose.

Conclusions

We observed that mRNA boosters after a primary vaccination course with either mRNA or viral-vector vaccines provided modest, short-lived protection against symptomatic infection with Omicron but substantial and more sustained protection against severe COVID-19 outcomes for at least 3 months.

Abstract

In a test-negative design case-control study, Dr. Thiago Cerqueira-Silva and colleagues, investigate the effectiveness of mRNA boosters after homologous primary series with BNT162b2 or ChAdOx1 against symptomatic infection and severe COVID-19 in Brazil and Scotland.

Author summary

Why was this study done?

Brazil and Scotland have been offering boosters for the population that received two doses of vaccines against the coronavirus that causes Coronavirus Disease 2019 (COVID-19). However, after Omicron (a SARS-CoV-2 variant) emerged, both countries reported a high number of COVID-19 cases despite accelerating their booster programs.
Knowledge about the duration of the protection offered by the booster doses is essential to guide public health recommendations.

What did the researchers do and find?

We analyzed national databases from Brazil and Scotland between January and April 2022 to estimate the protection offered by mRNA booster doses in individuals who received a primary series of viral vector or mRNA anti-COVID-19 vaccines.
For individuals that received primary series of viral vector vaccine plus mRNA booster, from 14 to 29 days to ≥4 months after the booster dose, vaccine effectiveness (VE) against symptomatic infection decreased significantly in Brazil from 51.6%, 95% confidence interval (CI): [51.0, 52.2], to 4.2% (95% CI: [0.7, 7.6], p = 0.02) and in Scotland from 67.1% (95% CI [65.5, 68.5], p < 0.001) to 37.4% (95% CI [33.8, 40.9], p < 0.001).
In these periods, a slight decrease in VE was observed against severe outcomes in Brazil from 93.5% (95% CI [93.0, 94.0], p < 0.001) to 82.3% (95% CI [79.7, 84.7], p < 0.001) and in Scotland from 98.3% (95% CI [87.3, 99.8], p < 0.001) to 77.8% (95% CI [51.4, 89.9], p < 0.001). Similar results were obtained with a homologous booster after a primary series of mRNA vaccines.
Similar findings in two very different countries allow us to draw reliable results because of potential sources of bias in effectiveness studies, such as differences in testing behavior and unmeasured characteristics between vaccinated and unvaccinated individuals, which are unrelated in the two countries.

What do these findings mean?

Modest, short-lived protection was observed against symptomatic infection caused by the Omicron variant after two doses of either vector viral or mRNA vaccine plus a booster dose with mRNA vaccine. However, protection against hospitalization or death was substantial for at least 3 months.

Related collections

Most cited references 29

Record: found
Abstract: found
Article: not found

Covid-19 Vaccine Effectiveness against the Omicron (B.1.1.529) Variant

Nick Andrews, Julia Stowe, Freja Kirsebom … (2022)

Background A rapid increase in coronavirus disease 2019 (Covid-19) cases due to the omicron (B.1.1.529) variant of severe acute respiratory syndrome coronavirus 2 in highly vaccinated populations has aroused concerns about the effectiveness of current vaccines. Methods We used a test-negative case–control design to estimate vaccine effectiveness against symptomatic disease caused by the omicron and delta (B.1.617.2) variants in England. Vaccine effectiveness was calculated after primary immunization with two doses of BNT162b2 (Pfizer–BioNTech), ChAdOx1 nCoV-19 (AstraZeneca), or mRNA-1273 (Moderna) vaccine and after a booster dose of BNT162b2, ChAdOx1 nCoV-19, or mRNA-1273. Results Between November 27, 2021, and January 12, 2022, a total of 886,774 eligible persons infected with the omicron variant, 204,154 eligible persons infected with the delta variant, and 1,572,621 eligible test-negative controls were identified. At all time points investigated and for all combinations of primary course and booster vaccines, vaccine effectiveness against symptomatic disease was higher for the delta variant than for the omicron variant. No effect against the omicron variant was noted from 20 weeks after two ChAdOx1 nCoV-19 doses, whereas vaccine effectiveness after two BNT162b2 doses was 65.5% (95% confidence interval [CI], 63.9 to 67.0) at 2 to 4 weeks, dropping to 8.8% (95% CI, 7.0 to 10.5) at 25 or more weeks. Among ChAdOx1 nCoV-19 primary course recipients, vaccine effectiveness increased to 62.4% (95% CI, 61.8 to 63.0) at 2 to 4 weeks after a BNT162b2 booster before decreasing to 39.6% (95% CI, 38.0 to 41.1) at 10 or more weeks. Among BNT162b2 primary course recipients, vaccine effectiveness increased to 67.2% (95% CI, 66.5 to 67.8) at 2 to 4 weeks after a BNT162b2 booster before declining to 45.7% (95% CI, 44.7 to 46.7) at 10 or more weeks. Vaccine effectiveness after a ChAdOx1 nCoV-19 primary course increased to 70.1% (95% CI, 69.5 to 70.7) at 2 to 4 weeks after an mRNA-1273 booster and decreased to 60.9% (95% CI, 59.7 to 62.1) at 5 to 9 weeks. After a BNT162b2 primary course, the mRNA-1273 booster increased vaccine effectiveness to 73.9% (95% CI, 73.1 to 74.6) at 2 to 4 weeks; vaccine effectiveness fell to 64.4% (95% CI, 62.6 to 66.1) at 5 to 9 weeks. Conclusions Primary immunization with two doses of ChAdOx1 nCoV-19 or BNT162b2 vaccine provided limited protection against symptomatic disease caused by the omicron variant. A BNT162b2 or mRNA-1273 booster after either the ChAdOx1 nCoV-19 or BNT162b2 primary course substantially increased protection, but that protection waned over time. (Funded by the U.K. Health Security Agency.)

0 comments Cited 1149 times – based on 0 reviews      Review now

Bookmark

Record: found
Abstract: found
Article: not found

Waning Immune Humoral Response to BNT162b2 Covid-19 Vaccine over 6 Months

Einav Levin, Yaniv Lustig, Carmit Cohen … (2021)

Background Despite high vaccine coverage and effectiveness, the incidence of symptomatic infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been increasing in Israel. Whether the increasing incidence of infection is due to waning immunity after the receipt of two doses of the BNT162b2 vaccine is unclear. Methods We conducted a 6-month longitudinal prospective study involving vaccinated health care workers who were tested monthly for the presence of anti-spike IgG and neutralizing antibodies. Linear mixed models were used to assess the dynamics of antibody levels and to determine predictors of antibody levels at 6 months. Results The study included 4868 participants, with 3808 being included in the linear mixed-model analyses. The level of IgG antibodies decreased at a consistent rate, whereas the neutralizing antibody level decreased rapidly for the first 3 months with a relatively slow decrease thereafter. Although IgG antibody levels were highly correlated with neutralizing antibody titers (Spearman’s rank correlation between 0.68 and 0.75), the regression relationship between the IgG and neutralizing antibody levels depended on the time since receipt of the second vaccine dose. Six months after receipt of the second dose, neutralizing antibody titers were substantially lower among men than among women (ratio of means, 0.64; 95% confidence interval [CI], 0.55 to 0.75), lower among persons 65 years of age or older than among those 18 to less than 45 years of age (ratio of means, 0.58; 95% CI, 0.48 to 0.70), and lower among participants with immunosuppression than among those without immunosuppression (ratio of means, 0.30; 95% CI, 0.20 to 0.46). Conclusions Six months after receipt of the second dose of the BNT162b2 vaccine, humoral response was substantially decreased, especially among men, among persons 65 years of age or older, and among persons with immunosuppression.

0 comments Cited 899 times – based on 0 reviews      Review now

Bookmark

Record: found
Abstract: found
Article: not found

Protection of BNT162b2 Vaccine Booster against Covid-19 in Israel

Yinon Bar-On, Yair Goldberg, Micha Mandel … (2021)

Background On July 30, 2021, the administration of a third (booster) dose of the BNT162b2 messenger RNA vaccine (Pfizer–BioNTech) was approved in Israel for persons who were 60 years of age or older and who had received a second dose of vaccine at least 5 months earlier. Data are needed regarding the effect of the booster dose on the rate of confirmed coronavirus 2019 disease (Covid-19) and the rate of severe illness. Methods We extracted data for the period from July 30 through August 31, 2021, from the Israeli Ministry of Health database regarding 1,137,804 persons who were 60 years of age or older and had been fully vaccinated (i.e., had received two doses of BNT162b2) at least 5 months earlier. In the primary analysis, we compared the rate of confirmed Covid-19 and the rate of severe illness between those who had received a booster injection at least 12 days earlier (booster group) and those who had not received a booster injection (nonbooster group). In a secondary analysis, we evaluated the rate of infection 4 to 6 days after the booster dose as compared with the rate at least 12 days after the booster. In all the analyses, we used Poisson regression after adjusting for possible confounding factors. Results At least 12 days after the booster dose, the rate of confirmed infection was lower in the booster group than in the nonbooster group by a factor of 11.3 (95% confidence interval [CI], 10.4 to 12.3); the rate of severe illness was lower by a factor of 19.5 (95% CI, 12.9 to 29.5). In a secondary analysis, the rate of confirmed infection at least 12 days after vaccination was lower than the rate after 4 to 6 days by a factor of 5.4 (95% CI, 4.8 to 6.1). Conclusions In this study involving participants who were 60 years of age or older and had received two doses of the BNT162b2 vaccine at least 5 months earlier, we found that the rates of confirmed Covid-19 and severe illness were substantially lower among those who received a booster (third) dose of the BNT162b2 vaccine.

0 comments Cited 634 times – based on 0 reviews      Review now

Bookmark

All references

Author and article information

Contributors

Thiago Cerqueira-Silva:

ORCID: https://orcid.org/0000-0003-4534-2509

Role: Formal analysisRole: InvestigationRole: MethodologyRole: Writing – original draftRole: Writing – review & editing

Syed Ahmar Shah:

ORCID: https://orcid.org/0000-0001-5672-0443

Role: Writing – original draftRole: Writing – review & editing

Chris Robertson:

ORCID: https://orcid.org/0000-0001-6848-5241

Role: ConceptualizationRole: Formal analysisRole: InvestigationRole: Methodology

Mauro Sanchez:

ORCID: https://orcid.org/0000-0002-0472-1804

Role: Writing – original draft

Srinivasa Vittal Katikireddi:

ORCID: https://orcid.org/0000-0001-6593-9092

Role: ConceptualizationRole: InvestigationRole: MethodologyRole: Writing – review & editing

Vinicius de Araujo Oliveira:

ORCID: https://orcid.org/0000-0001-7858-9650

Role: Data curationRole: Resources

Enny S. Paixão:

ORCID: https://orcid.org/0000-0002-4797-908X

Role: Writing – review & editing

Igor Rudan: Role: Writing – review & editing

Juracy Bertoldo Junior: Role: Software

Gerson O. Penna: Role: Writing – review & editing

Neil Pearce: Role: MethodologyRole: Writing – review & editing

Guilherme Loureiro Werneck:

ORCID: https://orcid.org/0000-0003-1169-1436

Role: Writing – review & editing

Mauricio L. Barreto: Role: Writing – review & editing

Viviane S. Boaventura:

ORCID: https://orcid.org/0000-0002-7241-6844

Role: InvestigationRole: SupervisionRole: Writing – original draftRole: Writing – review & editing

Aziz Sheikh: Role: ConceptualizationRole: Funding acquisitionRole: Project administrationRole: SupervisionRole: Writing – review & editing

Manoel Barral-Netto:

ORCID: https://orcid.org/0000-0002-5823-7903

Role: ConceptualizationRole: Funding acquisitionRole: Project administrationRole: ResourcesRole: SupervisionRole: Writing – review & editing

Amitabh Bipin Suthar: Role: Academic Editor

Journal

Journal ID (nlm-ta): PLoS Med

Journal ID (iso-abbrev): PLoS Med

Journal ID (publisher-id): plos

Title: PLOS Medicine

Publisher: Public Library of Science (San Francisco, CA USA )

ISSN (Print): 1549-1277

ISSN (Electronic): 1549-1676

Publication date (Electronic): 11 January 2023

Publication date Collection: January 2023

Volume: 20

Issue: 1

Electronic Location Identifier: e1004156

Affiliations

[1 ] LIB and LEITV Laboratories, Instituto Gonçalo Moniz, Fiocruz, Salvador, Bahia, Brazil

[2 ] Universidade Federal de Bahia (UFBA), Salvador, Bahia, Brazil

[3 ] Usher Institute, University of Edinburgh, Edinburgh, United Kingdom

[4 ] Public Health Scotland, Glasgow, United Kingdom

[5 ] Department of Mathematics and Statistics, University of Strathclyde, Glasgow, United Kingdom

[6 ] Universidade de Brasília, Brasília, Distrito Federal, Brazil

[7 ] MRC/CSO Social & Public Health Sciences Unit, University of Glasgow, Glasgow, United Kingdom

[8 ] Center for Data Integration and Knowledge for Health (Cidacs), Instituto Gonçalo Moniz, Fiocruz, Salvador, Bahia, Brazil

[9 ] London School of Hygiene and Tropical Medicine, London, United Kingdom

[10 ] Universidade do Estado do Rio de Janeiro, Rio de Janeiro, Brazil

[11 ] Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil

PLOS Medicine Editorial Board, UNITED STATES

Author notes

I have read the journal’s policy and the authors of this manuscript have the following competing interests: VdAO, VB, MLB, and MB-N are employees of Fiocruz, a federal public institution, which manufactures Vaxzevria in Brazil, through a full technology transfer agreement with AstraZeneca. Fiocruz allocates all its manufactured products to the Ministry of Health for the public health service use. SVK was a member of the UK Government’s Scientific Advisory Group on Emergencies subgroup on ethnicity, the Cabinet Office’s International Best Practice Advisory Group, and was co-chair of the Scottish Government’s Expert Reference Group on Ethnicity and COVID-19. CR is a member of the Scottish Government Chief Medical Officer’s COVID-19 Advisory Group, Scientific Pandemic Influenza Group on Modelling, and Medicines and Healthcare products Regulatory Agency Vaccine Benefit and Risk Working Group. CR reports the followings: “Research Grants to Strathclyde University from Public Health Scotland, UK Medical Research Council, Scotland Chief Scientist Office, Health Data Research UK. Advisory Bodies: Member of UK SPI-M committee, Scottish Government Scientific Advisory Committee, MHRA Covid vaccine benefit and risk expert working group.” IR is the member of the Advisory scientific committee on COVID-19 of the Government of Croatia and co-Editor-in-Chief of the Journal of Global Health. AS is an Academic Editor on PLOS Medicine’s editorial board, and is a member of the Scottish Government Chief Medical Officer’s COVID-19 Advisory Group and its Standing Committee on Pandemics; he is also a member of the UK Government’s New and Emerging Respiratory Virus Threats Risk Stratification Subgroup and a member of AstraZeneca’s Thrombotic Thrombocytopenic Taskforce. All roles are unremunerated. All other authors declare no competing interests.

‡ TCS, SAS, and CR share first authorship on this work. VSB, AS and MB-N are joint senior authors on this work.

* E-mail: manoel.barral@ 123456fiocruz.br

Author information

Thiago Cerqueira-Silva https://orcid.org/0000-0003-4534-2509

Syed Ahmar Shah https://orcid.org/0000-0001-5672-0443

Chris Robertson https://orcid.org/0000-0001-6848-5241

Mauro Sanchez https://orcid.org/0000-0002-0472-1804

Srinivasa Vittal Katikireddi https://orcid.org/0000-0001-6593-9092

Vinicius de Araujo Oliveira https://orcid.org/0000-0001-7858-9650

Enny S. Paixão https://orcid.org/0000-0002-4797-908X

Guilherme Loureiro Werneck https://orcid.org/0000-0003-1169-1436

Viviane S. Boaventura https://orcid.org/0000-0002-7241-6844

Manoel Barral-Netto https://orcid.org/0000-0002-5823-7903

Article

Publisher ID: PMEDICINE-D-22-01640

DOI: 10.1371/journal.pmed.1004156

PMC ID: 9879484

PubMed ID: 36630477

SO-VID: d60fd3ef-e774-45ec-96ba-aee0e6f6383d

License:

This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

History

Date received : 16 May 2022

Date accepted : 13 December 2022

Page count

Figures: 2, Tables: 1, Pages: 15

Funding

Funded by: Fiocruz

Award ID: VigiVac project

Funded by: JBS

Award ID: "Fazer o Bem Faz Bem" programme

Funded by: FAPESB

Award ID: PNX0008/2014

Award Recipient :

ORCID: https://orcid.org/0000-0002-5823-7903

Manoel Barral-Netto

Funded by: FAPERJ

Award ID: E-26/210.180/2020

Award Recipient :

ORCID: https://orcid.org/0000-0003-1169-1436

Guilherme Loureiro Werneck

Funded by: MRC

Award ID: MC_PC_19075

Funded by: UK Research and Innovation

Award ID: MC_PC_20058

Award Recipient : Aziz Sheikh

Funded by: Public Health Scotland and Scottish Government Director General Health and Social Care

Funded by: National Institute for Health Research

Award ID: 11/46/23

Award Recipient : Aziz Sheikh

Funded by: NIHR

Award ID: GHRG /16/137/99

Funded by: NHS Research Scotland

Award ID: SCAF/15/02

Award Recipient :

ORCID: https://orcid.org/0000-0001-6593-9092

Srinivasa Vittal Katikireddi

Funded by: MRC

Award ID: MC_UU_00022/2

Award Recipient :

ORCID: https://orcid.org/0000-0001-6593-9092

Srinivasa Vittal Katikireddi

Funded by: Scottish Government Chief Scientist Office

Award ID: SPHSU17

Award Recipient :

ORCID: https://orcid.org/0000-0001-6593-9092

Srinivasa Vittal Katikireddi

Funded by: National Institute for Health Research

Award ID: GHRG /16/137/99

The present study was suported by Fiocruz and partly supported by a donation from the "Fazer o Bem Faz Bem" programme from JBS S.A. MB-N received a grant from Fundação de Apoio do Estado da Bahia (FAPESB) – Grant PNX0008/2014/ Fapesb, Edital 08/2014 - Programa de Apoio a Núcleos de Excelência. GLW acknowledges Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro (E-26/210.180/2020). This study is part of the EAVE II project. EAVE II is funded by the MRC (MC_PC_19075) (AS, SVK, CR) with the support of BREATHE—The Health Data Research Hub for Respiratory Health (MC_PC_19004) (AS), which is funded through the UK Research and Innovation Industrial Strategy Challenge Fund and delivered through Health Data Research UK. This research is part of the Data and Connectivity National Core Study, led by Health Data Research UK in partnership with the Office for National Statistics and funded by UK Research and Innovation (grant ref MC_PC_20058) (AS, SVK, CR). Additional support has been provided through Public Health Scotland and Scottish Government Director General Health and Social Care and National Core Studies - Immunology. The original EAVE project was funded by the National Institute for Health Research (NIHR) Health Technology Assessment programme (11/46/23) (AS). The Brazilian component is part of the Fiocruz VigiVac project on continuous digital evaluation of the national anti-COVID-19 immunization programme. SVK acknowledges funding from an NHS Research Scotland Senior Clinical Fellowship (SCAF/15/02), the MRC (MC_UU_00022/2), and the Scottish Government Chief Scientist Office (SPHSU17). CR reports grants from the Medical Research Council (MRC) and Public Health Scotland during the conduct of the study. ESP is funded by the Wellcome Trust [Grant number 213589/Z/18/Z]. This partnership between Brazil and Scotland was established through funding from the NIHR (GHRG /16/137/99) using UK aid from the UK Government to support global health research(AS, SVK, CR, IR). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Custom metadata

PLOS Publication Stage vor-update-to-uncorrected-proof

Publication Update 2023-01-26

Data Availability Regarding Brazilian data availability, one of the study coordinators (M.B.-N.) signed a term of responsibility on using each database made available by the Ministry of Health (MoH). Each member of the research team signed a term of confidentiality before accessing the data. Data was manipulated in a secure computing environment, ensuring protection against data leakage. The Brazilian National Commission in Research Ethics approved the research protocol (CONEP approval no. 4.921.308). Our agreement with the MoH for accessing the databases patently denies authorization of access to a third party. Any information for assessing the databases must be addressed to the Brazilian MoH at https://datasus.saude.gov.br/, and requests can be addressed to datasus@ 123456saude.gov.br . In this study, we used anonymized secondary data following the Brazilian Personal Data Protection General Law, but it is vulnerable to re-identification by third parties as they contain dates of relevant health events regarding the same person. To protect the research participants’ privacy, the approved Research Protocol (CONEP approval no. 4.921.308) authorises the dissemination only of aggregated data, such as the data presented here. Regarding Scotland, the data that support the findings of this study are not publicly available because they are based on de-identified national clinical records. These are, however, available by application via Scotland’s National Safe Haven from Public Health Scotland. The data used in this study can be accessed by researchers through NHS Scotland’s Public Benefit and Privacy Panel via its Electronic Data Research and Innovation Service.

Outbreaks COVID-19

ScienceOpen disciplines: Medicine

Data availability:

ScienceOpen disciplines: Medicine

Comments

Comment on this article

scite_

Smart Citations

Citing PublicationsSupportingMentioningContrasting

View Citations

See how this article has been cited at scite.ai

scite shows how a scientific paper has been cited by providing the context of the citation, a classification describing whether it supports, mentions, or contrasts the cited claim, and a label indicating in which section the citation was made.

Cited by 6

See all cited by

Most referenced authors 814

See all reference authors

Effectiveness of mRNA boosters after homologous primary series with BNT162b2 or ChAdOx1 against symptomatic infection and severe COVID-19 in Brazil and Scotland: A test-negative design case–control study

Read this article at

Abstract

Background

Methods and findings

Conclusions

Abstract

Author summary

Why was this study done?

What did the researchers do and find?

What do these findings mean?

Related collections

Novel Coronavirus Disease COVID-19

Most cited references 29

Covid-19 Vaccine Effectiveness against the Omicron (B.1.1.529) Variant

Waning Immune Humoral Response to BNT162b2 Covid-19 Vaccine over 6 Months

Protection of BNT162b2 Vaccine Booster against Covid-19 in Israel

Author and article information

Contributors

Journal

Affiliations

Author notes

Author information

Article

History

Page count

Funding

Categories

Custom metadata

Comments

Comment on this article

Similar content 434

Cited by 6

Most referenced authors 814