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A. Koen · SciRah

Researcher profile · Semantic Scholar

A. Koen

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A. Koen — researcher profile on SciRah

h-index: 23
Works: 53
Citations: 7,707

Most-cited papers

Safety and efficacy of the ChAdOx1 nCoV-19 vaccine (AZD1222) against SARS-CoV-2: an interim analysis of four randomised controlled trials in Brazil, South Africa, and the UK
M. Voysey, S. A. Clemens, S. Madhi, L. Weckx +78 more
2020The Lancet4,063 citations Open access
Semantic Scholar
Single-dose administration and the influence of the timing of the booster dose on immunogenicity and efficacy of ChAdOx1 nCoV-19 (AZD1222) vaccine: a pooled analysis of four randomised trials
M. Voysey, S. A. Costa Clemens, S. Madhi, L. Weckx +76 more
2021The Lancet1,060 citations Open access
Semantic Scholar
ChAdOx1 nCoV-19 (AZD1222) Covid-19 vaccine efficacy against the B.1.351 variant
S. Madhi, V. Baillie, C. Cutland, M. Voysey +47 more
2021New England Journal of Medicine1,047 citations Open access
Semantic Scholar
Safety and immunogenicity of an investigational maternal trivalent group B streptococcus vaccine in healthy women and their infants: a randomised phase 1b/2 trial.
S. Madhi, C. Cutland, L. Jose, A. Koen +8 more
2016Lancet. Infectious Diseases (Print)154 citations
Semantic Scholar
Group B streptococcus vaccination in pregnant women with or without HIV in Africa: a non-randomised phase 2, open-label, multicentre trial
R. Heyderman, S. Madhi, N. French, C. Cutland +9 more
2016Lancet. Infectious Diseases (Print)119 citations Open access
Semantic Scholar
Safety and immunogenicity of the ChAdOx1 nCoV-19 (AZD1222) vaccine against SARS-CoV-2 in people living with and without HIV in South Africa: an interim analysis of a randomised, double-blind, placebo-controlled, phase 1B/2A trial
S. Madhi, A. Koen, A. Izu, L. Fairlie +34 more
2021The Lancet HIV112 citations Open access
Semantic Scholar
Safety and immunogenicity of a parenteral P2-VP8-P[8] subunit rotavirus vaccine in toddlers and infants in South Africa: a randomised, double-blind, placebo-controlled trial
M. Groome, A. Koen, A. Fix, N. Page +8 more
2017Lancet. Infectious Diseases (Print)111 citations Open access
Semantic Scholar
Trivalent inactivated influenza vaccine in African adults infected with human immunodeficient virus: double blind, randomized clinical trial of efficacy, immunogenicity, and safety.
S. Madhi, M. Maskew, A. Koen, L. Kuwanda +6 more
2011Clinical Infectious Diseases106 citations
Semantic Scholar
Safety and efficacy of the ChAdOx1 nCoV-19 (AZD1222) Covid-19 vaccine against the B.1.351 variant in South Africa
S. Madhi, V. Baillie, C. Cutland, M. Voysey +47 more
2021medRxiv98 citations Open access
Semantic Scholar
Burden of Invasive Group B Streptococcus Disease and Early Neurological Sequelae in South African Infants
Z. Dangor, S. Lala, C. Cutland, A. Koen +6 more
2015PLoS ONE88 citations Open access
Semantic Scholar
Effect of breastfeeding on immunogenicity of oral live-attenuated human rotavirus vaccine: a randomized trial in HIV-uninfected infants in Soweto, South Africa.
M. Groome, Sung-Sil Moon, Daniel E Velasquez, Stephanie A. Jones +5 more
2014Bulletin of the World Health Organization87 citations Open access
Semantic Scholar
Preliminary Efficacy of the NVX-CoV2373 Covid-19 Vaccine Against the B.1.351 Variant
V. Shinde, Sutika Bhikha, Z. Hoosain, M. Archary +45 more
2021medRxiv72 citations Open access
Semantic Scholar
Safety and immunogenicity of a parenteral trivalent P2-VP8 subunit rotavirus vaccine: a multisite, randomised, double-blind, placebo-controlled trial
M. Groome, L. Fairlie, J. Morrison, A. Fix +11 more
2020Lancet. Infectious Diseases (Print)62 citations Open access
Semantic Scholar
Safety and immunogenicity of VPM1002 versus BCG in South African newborn babies: a randomised, phase 2 non-inferiority double-blind controlled trial.
M. Cotton, S. Madhi, A. Luabeya, M. Tameris +22 more
2022Lancet. Infectious Diseases (Print)58 citations
Semantic Scholar
Antibody Kinetics and Response to Routine Vaccinations in Infants Born to Women Who Received an Investigational Trivalent Group B Streptococcus Polysaccharide CRM197-Conjugate Vaccine During Pregnancy
S. Madhi, A. Koen, C. Cutland, L. Jose +8 more
2017Clinical Infectious Diseases53 citations Open access
Semantic Scholar
Acquisition of Streptococcus pneumoniae in Pneumococcal Conjugate Vaccine-naïve South African Children and Their Mothers
M. Nunes, T. Shiri, N. van Niekerk, C. Cutland +7 more
2013The Pediatric Infectious Disease Journal37 citations Open access
Semantic Scholar
Novavax NVX-COV2373 triggers neutralization of Omicron sub-lineages
J. Bhiman, S. Richardson, B. Lambson, P. Kgagudi +26 more
2023Scientific Reports36 citations Open access
Semantic Scholar
Single Dose Administration, And The Influence Of The Timing Of The Booster Dose On Immunogenicity and Efficacy Of ChAdOx1 nCoV-19 (AZD1222) Vaccine
M. Voysey, S. A. Costa Clemens, S. Madhi, L. Weckx +74 more
2021Social Science Research Network36 citations Open access
Semantic Scholar
(2021). Safety and efficacy of the ChAdOx1 nCoV-19 vaccine (AZD1222) against SARS-CoV-2: an interim analysis of four randomised controlled trials in Brazil, South Africa, and the UK. The Lancet, 397(10269), 99-111.
S. C. Clemens, S. Madhi, L. Weckx, P. Folegatti +59 more
202035 citations
Semantic Scholar
Safety and immunogenicity of a plant-derived rotavirus-like particle vaccine in adults, toddlers and infants.
Natsuki Kurokawa, Michelle Robinson, C. Bernard, Y. Kawaguchi +10 more
2021Vaccine28 citations
Semantic Scholar
Safety and Pharmacokinetics of Nirsevimab in Immunocompromised Children.
Joseph B. Domachowske, U. W. Hamrén, Irfana Banu, R. Baronio +9 more
2024Pediatrics25 citations Open access
Semantic Scholar
Antibody Persistence and Booster Vaccination of a Fully Liquid Hexavalent Vaccine Coadministered With Measles/Mumps/Rubella and Varicella Vaccines at 15–18 Months of Age in Healthy South African Infants
S. Madhi, A. Koen, C. Cutland, M. Groome +1 more
2013The Pediatric Infectious Disease Journal25 citations Open access
Semantic Scholar
ChAdOx1 nCoV-19 (AZD1222) vaccine-induced Fc receptor binding tracks with differential susceptibility to COVID-19
P. Kaplonek, D. Cizmeci, G. Kwatra, A. Izu +24 more
2023Nature Immunology24 citations Open access
Semantic Scholar
Durability of ChAdOx1 nCoV-19 (AZD1222) vaccine and hybrid humoral immunity against variants including omicron BA.1 and BA.4 6 months after vaccination (COV005): a post-hoc analysis of a randomised, phase 1b–2a trial
S. Madhi, G. Kwatra, S. Richardson, A. Koen +33 more
2022Lancet. Infectious Diseases (Print)21 citations Open access
Semantic Scholar
Immunogenicity of Seven-Valent Pneumococcal Conjugate Vaccine Administered at 6, 14 and 40 Weeks of Age in South African Infants
Stephanie A. Jones, M. Groome, A. Koen, N. van Niekerk +5 more
2013PLoS ONE19 citations Open access
Semantic Scholar
Vaccination with 10-valent pneumococcal conjugate vaccine in infants according to HIV status
S. Madhi, A. Koen, L. Jose, N. van Niekerk +8 more
2017Medicine18 citations Open access
Semantic Scholar
Immunogenicity of a single-dose compared with a two-dose primary series followed by a booster dose of ten-valent or 13-valent pneumococcal conjugate vaccine in South African children: an open-label, randomised, non-inferiority trial
S. Madhi, E. Mutsaerts, A. Izu, Welekazi Boyce +11 more
2020Lancet. Infectious Diseases (Print)16 citations Open access
Semantic Scholar
Single priming and booster dose of ten-valent and 13-valent pneumococcal conjugate vaccines and Streptococcus pneumoniae colonisation in children in South Africa: a single-centre, open-label, randomised trial
C. Olwagen, A. Izu, E. Mutsaerts, L. Jose +9 more
2023The Lancet Child & Adolescent Health13 citations Open access
Semantic Scholar
Evaluation of Clinical Case Definitions for Respiratory Syncytial Virus Lower Respiratory Tract Infection in Young Children
J. Englund, Rachel A. Cohen, V. Bianco, J. Domachowske +21 more
2023Journal of the Pediatric Infectious Diseases Society13 citations Open access
Semantic Scholar
Novavax NVX-COV2373 triggers potent neutralization of Omicron sub-lineages
J. Bhiman, S. Richardson, B. Lambson, P. Kgagudi +26 more
2022bioRxiv12 citations Open access
Semantic Scholar
ChAdOx1 nCoV-19 (AZD1222) Vaccine in People Living With and Without HIV
S. Madhi, A. Koen, L. Fairlie, C. Cutland +33 more
20219 citations Open access
Semantic Scholar
Immunization with 10-valent pneumococcal non-typeable Haemophilus influenzae protein D conjugate vaccine (PHiD-CV) according to different schedules in infants in South Africa: a phase III trial
S. Madhi, A. Koen, L. Jose, M. Moreira +7 more
2017Expert Review of Vaccines9 citations Open access
Semantic Scholar
Immunogenicity and safety of an early measles vaccination schedule at 6 and 12 months of age in HIV-unexposed and HIV-exposed uninfected South African children.
E. Mutsaerts, M. Nunes, Sutika Bhikha, Benit T Ikulinda +8 more
2019Journal of Infectious Diseases8 citations Open access
Semantic Scholar
Efficacy of primary series AZD1222 (ChAdOx1 nCoV-19) vaccination against SARS-CoV-2 variants of concern: Final analysis of a randomized, placebo-controlled, phase 1b/2 study in South African adults (COV005)
A. Koen, A. Izu, V. Baillie, G. Kwatra +32 more
2023Vaccine6 citations Open access
Semantic Scholar
Impact of HIV status and vaccination schedule on bacterial nasopharyngeal carriage following infant immunisation with the pneumococcal non-typeable Haemophilus influenzae protein D conjugate vaccine in South Africa.
S. Madhi, M. Moreira, A. Koen, N. van Niekerk +9 more
2020Vaccine6 citations Open access
Semantic Scholar
Immunogenicity and safety of a hexavalent pediatric vaccine in HIV-exposed infected and uninfected infants in Republic of South Africa
A. Koen, S. Madhi, O. Lyabis, E. Vidor +4 more
2020Human Vaccines & Immunotherapeutics5 citations Open access
Semantic Scholar
Impact of nutritional status on vaccine-induced immunity in children living in South Africa: Investigating the B-cell repertoire and metabolic hormones.
E. Mutsaerts, B. van Cranenbroek, S. Madhi, E. Simonetti +6 more
2024Vaccine4 citations Open access
Semantic Scholar
T-cell responses induced by ChAdOx1 nCoV-19 (AZD1222) vaccine to wild-type severe acute respiratory syndrome coronavirus 2 among people with and without HIV in South Africa
William C. McMahon, G. Kwatra, A. Izu, A. Koen +13 more
2022AIDS (London)4 citations Open access
Semantic Scholar
HLA antibody repertoire in infants suggests selectivity in transplacental crossing
D. Savulescu, M. Groome, S. Malfeld, S. Madhi +6 more
2020American Journal of Reproductive Immunology4 citations Open access
Semantic Scholar
T-cell responses induced by SARS-CoV-2 index-virus nanoparticle protein vaccine to the ancestral and omicron variants 6 months following primary vaccination
William C. McMahon, G. Kwatra, Marta C. Nunes, A. Izu +7 more
2025Communications Medicine3 citations Open access
Semantic Scholar
Immunogenicity and Safety of SARS-CoV-2 Recombinant Spike Protein Vaccine in South African People Living With and Without HIV-1 Infection: A Phase 2 Randomised Trial.
C. Bennett, Z. Hoosain, A. Koen, Umesh Lalloo +8 more
2024Journal of Infection3 citations Open access
Semantic Scholar
Bacterial nasopharyngeal carriage following infant immunization with pneumococcal conjugate vaccines according to a 2+1 schedule in children in South Africa: an exploratory analysis of two clinical trials
M. Nunes, M. Moreira, A. Koen, N. van Niekerk +9 more
2020Expert Review of Vaccines3 citations Open access
Semantic Scholar
Neutrophil Counts in Healthy South African Infants: Implications for Enrollment and Adverse Event Grading in Clinical Trials in an African Setting
A. Koen, L. Jose, S. Madhi, A. Fix +2 more
2019The Journal of Pediatrics: X3 citations Open access
Semantic Scholar
Single priming and a booster dose of 10-valent and 13-valent pneumococcal conjugate vaccine (PCV) maintains suppression of vaccine serotype colonization in South African children at 3, 4, and 5 years of age: a single-centre, open-labelled, randomized trial
C. Olwagen, A. Izu, Lara Van der Merwe, L. Jose +2 more
2024Expert Review of Vaccines2 citations Open access
Semantic Scholar
Efficacy of the AZD1222 (ChAdOx1 nCoV-19) COVID-19 Vaccine Against SARS-CoV-2 Variants of Concern
A. Koen, A. Izu, V. Baillie, G. Kwatra +32 more
2022medRxiv2 citations Open access
Semantic Scholar
Short-term immunogenicity and safety of hepatitis-A and varicella vaccines in HIV-exposed uninfected and HIV-unexposed South African children.
E. Mutsaerts, M. Nunes, Sutika Bhikha, Benit T Ikulinda +7 more
2020Vaccine2 citations Open access
Semantic Scholar
Waning of measles immunity by 5 years of age following an accelerated two-dose measles vaccine schedule at 6 and 12 months in South African children: an observational cohort study.
Daniel Kapelus, Heena Ranchod, C. Olwagen, A. Koen +4 more
2026Vaccine1 citations Open access
Semantic Scholar
Serotype-specific serum immunoglobulin G at 18 months of age following one or two doses of a primary series of 10-valent or 13-valent pneumococcal conjugate vaccine and a booster dose at nine months of age: a randomized controlled study
A. Izu, E.A.M.L. Mutsaerts, C. Olwagen, L. Jose +4 more
2025Expert Review of Vaccines1 citations Open access
Semantic Scholar
Longitudinal IgA and IgG Response, and ACE2 Binding Blockade, to Full-Length SARS-CoV-2 Spike Protein Variants in a Population of Black PLWH Vaccinated with ChAdOx1 nCoV-19
Muneerah Smith, G. Kwatra, A. Izu, A. Nel +12 more
2023Viruses1 citations Open access
Semantic Scholar
Immunogenicity up to age 5 years following a single-dose or two-dose infant primary series of 10-valent or 13-valent pneumococcal conjugate vaccine each followed by a booster dose in South Africa: extended follow-up of a single-centre, open-label, non-inferiority, randomised controlled trial.
Daniel Kapelus, C. Olwagen, A. Izu, Heena Ranchod +8 more
2026The Lancet Child & Adolescent Health0 citations
Semantic Scholar

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