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. 2023 Sep;17(9):e13173.
doi: 10.1111/irv.13173.

SARS-CoV-2 seroprevalence and implications for population immunity: Evidence from two Health and Demographic Surveillance System sites in Kenya, February-December 2022

E Wangeci Kagucia  1 , Abdhala K Ziraba  2 , James Nyagwange  1 , Bernadette Kutima  1 , Makobu Kimani  1 , Donald Akech  1 , Maurine Ng'oda  2 , Antipa Sigilai  1 , Daisy Mugo  1 , Henry Karanja  1 , John Gitonga  1 , Angela Karani  1 , Monica Toroitich  1 , Boniface Karia  1 , Mark Otiende  1 , Anne Njeri  2 , Rashid Aman  3 , Patrick Amoth  3 , Mercy Mwangangi  3 , Kadondi Kasera  3 , Wangari Ng'ang'a  4 , Shirine Voller  1   5 , Lynette I Ochola-Oyier  1 , Christian Bottomley  5 , Amek Nyaguara  1 , Patrick K Munywoki  6 , Godfrey Bigogo  7 , Eric Maitha  8 , Sophie Uyoga  1 , Katherine E Gallagher  1   5 , Anthony O Etyang  1 , Edwine Barasa  1 , Joseph Mwangangi  1 , Philip Bejon  1   9 , Ifedayo M O Adetifa  1   5 , George M Warimwe  1   9 , J Anthony G Scott  1   5 , Ambrose Agweyu  1   5
Affiliations

SARS-CoV-2 seroprevalence and implications for population immunity: Evidence from two Health and Demographic Surveillance System sites in Kenya, February-December 2022

E Wangeci Kagucia et al. Influenza Other Respir Viruses. 2023 Sep.

Abstract

Background: We sought to estimate SARS-CoV-2 antibody seroprevalence within representative samples of the Kenyan population during the third year of the COVID-19 pandemic and the second year of COVID-19 vaccine use.

Methods: We conducted cross-sectional serosurveys among randomly selected, age-stratified samples of Health and Demographic Surveillance System (HDSS) residents in Kilifi and Nairobi. Anti-spike (anti-S) immunoglobulin G (IgG) serostatus was measured using a validated in-house ELISA and antibody concentrations estimated with reference to the WHO International Standard for anti-SARS-CoV-2 immunoglobulin.

Results: HDSS residents were sampled in February-June 2022 (Kilifi HDSS N = 852; Nairobi Urban HDSS N = 851) and in August-December 2022 (N = 850 for both sites). Population-weighted coverage for ≥1 doses of COVID-19 vaccine were 11.1% (9.1-13.2%) among Kilifi HDSS residents by November 2022 and 34.2% (30.7-37.6%) among Nairobi Urban HDSS residents by December 2022. Population-weighted anti-S IgG seroprevalence among Kilifi HDSS residents increased from 69.1% (65.8-72.3%) by May 2022 to 77.4% (74.4-80.2%) by November 2022. Within the Nairobi Urban HDSS, seroprevalence by June 2022 was 88.5% (86.1-90.6%), comparable with seroprevalence by December 2022 (92.2%; 90.2-93.9%). For both surveys, seroprevalence was significantly lower among Kilifi HDSS residents than among Nairobi Urban HDSS residents, as were antibody concentrations (p < 0.001).

Conclusion: More than 70% of Kilifi residents and 90% of Nairobi residents were seropositive for anti-S IgG by the end of 2022. There is a potential immunity gap in rural Kenya; implementation of interventions to improve COVID-19 vaccine uptake among sub-groups at increased risk of severe COVID-19 in rural settings is recommended.

Keywords: COVID-19; Health and Demographic Surveillance System; IgG antibody; Kenya; SARS-CoV-2; seroprevalence.

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Conflict of interest statement

The authors declare no conflicts of interest.

Figures

FIGURE 1
FIGURE 1
Study participant flow.
FIGURE 2
FIGURE 2
Population‐weighted anti‐spike IgG seroprevalence among all study participants by site, sex, and age category.
FIGURE 3
FIGURE 3
Reverse cumulative distribution curves of anti‐S IgG concentrations within the Kilifi Health and Demographic Surveillance System (HDSS) and Nairobi Urban HDSS. The red vertical line represents an antibody concentration of 154 binding antibody units per milliliter.
FIGURE 4
FIGURE 4
Population‐weighted and test‐adjusted anti‐nucleoprotein IgG seroprevalence among study participants overall and by COVID‐19 vaccination status, sex, and age category within the (A) Kilifi Health and Demographic Surveillance System (HDSS) and the (B) Nairobi Urban HDSS.
See this image and copyright information in PMC

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