Seroprevalence of anti-SARS-CoV-2 specific antibodies in vaccinated and vaccine naïve adult Nigerians

The effect of COVID vaccination timing on the seroprevalence of IgG antibodies: evidence from the Guayas region of Ecuador

Background and aims

Timely distribution of COVID-19 vaccines was particularly important for developing countries that do not have strong health systems and related infrastructure. We analyze data from the Guayas province of Ecuador, an area particularly affected by the pandemic, to determine the seroprevalence of SARS-CoV-2 and the effect of the timing of the second dose of COVID-19 vaccines on the seroprevalence SARS-CoV-2 IgG antibodies.

Methods

This cross-sectional study involved 1,761 individuals aged 18 and older who voluntarily enrolled prior to and during the initial phase of vaccine rollout in Ecuador (October 2020 to July 2022). IgG anti-SARS-CoV-2 RBD antibodies were assessed by an in-house ELISA to evaluate the immune response to Pfizer (BioNTech, Spike mRNA) and AstraZeneca (Oxford, AstraZeneca Spike) vaccine in the Guayas province. Ordinary least squares (OLS) regressions were employed to determine the effect of delayed second doses later than prescribed by the manufacturer for both vaccines.

Results

Before the vaccination campaign, we estimated an RBD IgG seroprevalence of 27.7% (95% CI: 23.6-27, n = 469). The estimate increased to 89.4% (95% CI: 87.7-91.18, n = 1,235) after the first vaccine dose and to 92.6% (95% CI: 90.7-94.5, n = 748) after the second dose. Individuals who received the second dose of the Pfizer vaccine later than the recommended dose showed significantly lower levels of IgG antibodies 2-3 weeks after receiving the second dose than those who received the dose within the recommended timeframe. Furthermore, we did not find any effect on RBD IgG antibody levels in those who received a second dose of the AstraZeneca vaccine during the first and second parts of the recommended vaccination window.

Conclusion

The results suggest that a significant portion of the study population was already infected with SARS-CoV-2 prior to the vaccination. As expected, seropositivity increased alongside vaccination efforts. We determined that Pfizer vaccine recipients should be adhered to vaccine timing guidelines. Furthermore, resource-limited countries should consider administering vaccines with flexibility in dosing intervals, such as AstraZeneca, as it allows for a wider time frame without significantly reducing the boosting of IgG antibodies.

Olawoye I, Akano K, Okolie J, Eromon P, Olaitan P, Olagunoye A, Adebayo I, Adebayo V, Babalola E, Abioye O, Ajayi N, Ogah E, Ukwaja K, Okoro S, Oje O, Kingsley OC, Eke M, Onyia V, Achonduh-Atijegbe O, Ewah FE, Obasi M, Igwe V, Ayodeji O, Chukwuyem A, Owhin S, Oyejide N, Abah S, Ingbian W, Osoba M, Alebiosu A, Nadesalingam A, Aguinam ET, Carnell G, Krause N, Chan A, George C, Kinsley R, Tonks P, Temperton N, Heeney J, Happi C. Immunological insights into COVID-19 in Southern Nigeria

Introduction

One of the unexpected outcomes of the COVID-19 pandemic was the relatively low levels of morbidity and mortality in Africa compared to the rest of the world. Nigeria, Africa's most populous nation, accounted for less than 0.01% of the global COVID-19 fatalities. The factors responsible for Nigeria's relatively low loss of life due to COVID-19 are unknown. Also, the correlates of protective immunity to SARS-CoV-2 and the impact of pre-existing immunity on the outcome of the COVID-19 pandemic in Africa are yet to be elucidated. Here, we evaluated the natural and vaccine-induced immune responses from vaccinated, non-vaccinated and convalescent individuals in Southern Nigeria throughout the three waves of the COVID-19 pandemic in Nigeria. We also examined the pre-existing immune responses to SARS-CoV-2 from samples collected prior to the COVID-19 pandemic.

Methods

We used spike RBD and N- IgG antibody ELISA to measure binding antibody responses, SARS-CoV-2 pseudotype assay protocol expressing the spike protein of different variants (D614G, Delta, Beta, Omicron BA1) to measure neutralizing antibody responses and nucleoprotein (N) and spike (S1, S2) direct ex vivo interferon gamma (IFNγ) T cell ELISpot to measure T cell responses.

Result

Our study demonstrated a similar magnitude of both binding (N-IgG (74% and 62%), S-RBD IgG (70% and 53%) and neutralizing (D614G (49% and 29%), Delta (56% and 47%), Beta (48% and 24%), Omicron BA1 (41% and 21%)) antibody responses from symptomatic and asymptomatic survivors in Nigeria. A similar magnitude was also seen among vaccinated participants. Interestingly, we revealed the presence of preexisting binding antibodies (N-IgG (60%) and S-RBD IgG (44%)) but no neutralizing antibodies from samples collected prior to the pandemic.

Discussion

These findings revealed that both vaccinated, non-vaccinated and convalescent individuals in Southern Nigeria make similar magnitude of both binding and cross-reactive neutralizing antibody responses. It supported the presence of preexisting binding antibody responses among some Nigerians prior to the COVID-19 pandemic. Lastly, hybrid immunity and heterologous vaccine boosting induced the strongest binding and broadly neutralizing antibody responses compared to vaccine or infection-acquired immunity alone.

Seroprevalence of SARS-CoV-2 anti-spike IgG antibody among COVID-19 vaccinated individuals residing in Surabaya, East Java, Indonesia

Background

To limit the SARS-CoV-2 transmission, the Indonesian government launched a COVID-19 vaccination program in January 2021. Studies on the clinical treatment and implementation of COVID-19 vaccination have shown promising results; however, it is necessary to estimate the effectiveness of the vaccines. With the ongoing COVID-19 pandemic, studies have highlighted the impact of COVID-19 vaccines, especially CoronaVac, on Indonesian healthcare workers. To get a better picture of how the vaccines work in Indonesia, it is necessary to estimate the prevalence of SARS-CoV-2 anti-S IgG antibody induced by the COVID-19 vaccine in individuals who have already received two-to-three doses of vaccines.

Materials and Methods

Four-hundred and ninety-six whole-blood samples were collected from participants residing in Surabaya, East Java, Indonesia, who received a minimum of a two-dose COVID-19 vaccine. Serums were then isolated from the blood and subjected to detect SARS-CoV-2 anti-S IgG antibodies using a lateral flow immunochromatographic assay.

Results

The prevalence of positive anti-S-IgG antibodies was 91.7% (455/496) in all participants receiving a minimum of a two-dose COVID-19 vaccine. As many as 209 (85.3%) and 141 (96.6%) participants were seropositive for receiving CoronaVac and AstraZeneca, respectively. Meanwhile, all participants receiving two-dose CoronaVac with one booster dose of Moderna (105/100%) were seropositive (p < 0.05). Age, comorbidity, and time after the last vaccine were significantly correlated with seropositivity (p < 0.05).

Conclusion

Different vaccines might produce different antibody responses. Adopting a stronger policy regarding the administration of booster doses might be beneficial to elicit positive anti-S-IgG antibodies, especially among older individuals, those with comorbid diseases, and those with a longer time after the second vaccination dose.