A repeated cross-sectional analysis of SARS-CoV-2 seroprevalence in Manila, the Philippines after implementation of the national COVID-19 vaccination program

Abstract Background SARS-CoV-2 seroepidemiological studies, which have been used to describe population-level immunity, are limited in the Philippines, despite the protracted course of the epidemic in the country. We follow-up on our previous work and aimed to estimate SARS-CoV-2 seroprevalence and...

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Main Authors: Greco Mark B. Malijan, Shuichi Suzuki, Ana Ria Sayo, Annavi Marie Villanueva, Kristal An Agrupis, Abigail Ortal-Cruz, Mary Ann Salazar, Jan Wendzl Evangelista, Rontgene Solante, Grace Devota Go, Naomi Ruth Saludar, Dinarazad Miranda, Alexis Dimapilis, Koya Ariyoshi, Chris Smith
Format: Article
Language:English
Published: BMC 2025-06-01
Series:Tropical Medicine and Health
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Online Access:https://doi.org/10.1186/s41182-025-00767-9
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author Greco Mark B. Malijan
Shuichi Suzuki
Ana Ria Sayo
Annavi Marie Villanueva
Kristal An Agrupis
Abigail Ortal-Cruz
Mary Ann Salazar
Jan Wendzl Evangelista
Rontgene Solante
Grace Devota Go
Naomi Ruth Saludar
Dinarazad Miranda
Alexis Dimapilis
Koya Ariyoshi
Chris Smith
author_facet Greco Mark B. Malijan
Shuichi Suzuki
Ana Ria Sayo
Annavi Marie Villanueva
Kristal An Agrupis
Abigail Ortal-Cruz
Mary Ann Salazar
Jan Wendzl Evangelista
Rontgene Solante
Grace Devota Go
Naomi Ruth Saludar
Dinarazad Miranda
Alexis Dimapilis
Koya Ariyoshi
Chris Smith
author_sort Greco Mark B. Malijan
collection DOAJ
description Abstract Background SARS-CoV-2 seroepidemiological studies, which have been used to describe population-level immunity, are limited in the Philippines, despite the protracted course of the epidemic in the country. We follow-up on our previous work and aimed to estimate SARS-CoV-2 seroprevalence and infection rate among outpatient clinic attendees in Metro Manila, a year after the implementation of the national COVID-19 vaccination program. Methods We conducted four repeated cross-sectional surveys at the outpatient department of San Lazaro Hospital between March 2022 and January 2023. We performed χ2 test and analysis of variance to assess the differences in characteristics across different data collection periods. Results A total of 765 participants were enrolled, ranging from 170 to 200 per period. Participant demographic, socioeconomic, and medical history were comparable across all data collection periods. Between March and October 2022, the proportion of participants who received a vaccine or booster dose significantly increased, from 77.9% to 90%. Seroprevalence across all data collection periods was consistently high, ranging from 97.8% to 99.5%. However, the geometric mean concentration of antibodies was highest in the data collection period following the Omicron-dominant wave. Infection rates were comparably low (< 10%) across periods, except for a peak at 16.7% in September to October 2022, which followed the rise in reported cases in Metro Manila. Conclusion Population-level seroprevalence among clinic attendees in Manila was consistently high a year after implementation of the national COVID-19 vaccination program, but analyses of antibody concentrations showed potential waning within a 3-month period.
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spelling doaj-art-cce884b2261c4afdbda72ecc3ceb92502025-08-20T03:47:17ZengBMCTropical Medicine and Health1349-41472025-06-0153111110.1186/s41182-025-00767-9A repeated cross-sectional analysis of SARS-CoV-2 seroprevalence in Manila, the Philippines after implementation of the national COVID-19 vaccination programGreco Mark B. Malijan0Shuichi Suzuki1Ana Ria Sayo2Annavi Marie Villanueva3Kristal An Agrupis4Abigail Ortal-Cruz5Mary Ann Salazar6Jan Wendzl Evangelista7Rontgene Solante8Grace Devota Go9Naomi Ruth Saludar10Dinarazad Miranda11Alexis Dimapilis12Koya Ariyoshi13Chris Smith14San Lazaro Hospital – Nagasaki University Collaborative Research Office, San Lazaro HospitalSan Lazaro Hospital – Nagasaki University Collaborative Research Office, San Lazaro HospitalSan Lazaro HospitalSan Lazaro HospitalSan Lazaro Hospital – Nagasaki University Collaborative Research Office, San Lazaro HospitalSan Lazaro Hospital – Nagasaki University Collaborative Research Office, San Lazaro HospitalSan Lazaro Hospital – Nagasaki University Collaborative Research Office, San Lazaro HospitalSan Lazaro Hospital – Nagasaki University Collaborative Research Office, San Lazaro HospitalSan Lazaro HospitalSan Lazaro HospitalSan Lazaro HospitalSan Lazaro HospitalSan Lazaro HospitalSchool of Tropical Medicine and Global Health, Nagasaki UniversitySchool of Tropical Medicine and Global Health, Nagasaki UniversityAbstract Background SARS-CoV-2 seroepidemiological studies, which have been used to describe population-level immunity, are limited in the Philippines, despite the protracted course of the epidemic in the country. We follow-up on our previous work and aimed to estimate SARS-CoV-2 seroprevalence and infection rate among outpatient clinic attendees in Metro Manila, a year after the implementation of the national COVID-19 vaccination program. Methods We conducted four repeated cross-sectional surveys at the outpatient department of San Lazaro Hospital between March 2022 and January 2023. We performed χ2 test and analysis of variance to assess the differences in characteristics across different data collection periods. Results A total of 765 participants were enrolled, ranging from 170 to 200 per period. Participant demographic, socioeconomic, and medical history were comparable across all data collection periods. Between March and October 2022, the proportion of participants who received a vaccine or booster dose significantly increased, from 77.9% to 90%. Seroprevalence across all data collection periods was consistently high, ranging from 97.8% to 99.5%. However, the geometric mean concentration of antibodies was highest in the data collection period following the Omicron-dominant wave. Infection rates were comparably low (< 10%) across periods, except for a peak at 16.7% in September to October 2022, which followed the rise in reported cases in Metro Manila. Conclusion Population-level seroprevalence among clinic attendees in Manila was consistently high a year after implementation of the national COVID-19 vaccination program, but analyses of antibody concentrations showed potential waning within a 3-month period.https://doi.org/10.1186/s41182-025-00767-9COVID-19PhilippinesSARS-CoV-2VaccinationSeroepidemiological study
spellingShingle Greco Mark B. Malijan
Shuichi Suzuki
Ana Ria Sayo
Annavi Marie Villanueva
Kristal An Agrupis
Abigail Ortal-Cruz
Mary Ann Salazar
Jan Wendzl Evangelista
Rontgene Solante
Grace Devota Go
Naomi Ruth Saludar
Dinarazad Miranda
Alexis Dimapilis
Koya Ariyoshi
Chris Smith
A repeated cross-sectional analysis of SARS-CoV-2 seroprevalence in Manila, the Philippines after implementation of the national COVID-19 vaccination program
Tropical Medicine and Health
COVID-19
Philippines
SARS-CoV-2
Vaccination
Seroepidemiological study
title A repeated cross-sectional analysis of SARS-CoV-2 seroprevalence in Manila, the Philippines after implementation of the national COVID-19 vaccination program
title_full A repeated cross-sectional analysis of SARS-CoV-2 seroprevalence in Manila, the Philippines after implementation of the national COVID-19 vaccination program
title_fullStr A repeated cross-sectional analysis of SARS-CoV-2 seroprevalence in Manila, the Philippines after implementation of the national COVID-19 vaccination program
title_full_unstemmed A repeated cross-sectional analysis of SARS-CoV-2 seroprevalence in Manila, the Philippines after implementation of the national COVID-19 vaccination program
title_short A repeated cross-sectional analysis of SARS-CoV-2 seroprevalence in Manila, the Philippines after implementation of the national COVID-19 vaccination program
title_sort repeated cross sectional analysis of sars cov 2 seroprevalence in manila the philippines after implementation of the national covid 19 vaccination program
topic COVID-19
Philippines
SARS-CoV-2
Vaccination
Seroepidemiological study
url https://doi.org/10.1186/s41182-025-00767-9
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