Situation Analysis of Immune Response Status One Year After the Nationwide COVID-19 Vaccination in Cameroon: Role of Obesity and SARS-CoV-2 Infection

Background and Aims

Vaccines have been developed to control the COVID-19 pandemic, but vaccine coverage is low in sub-Saharan Africa. This study aimed at analysing the anti-SARS-CoV-2 immune response among vaccinated individuals.

Methods

Between January and September 2022, a multicentre study took place in Douala, Cameroon. Blood samples were used for determining serum levels of anti-SARS-CoV-2 IgG and IgM antibodies, IL-6, IFN-γ, and CD4 + , while nasopharyngeal samples were used for molecular confirmation of SARS-CoV-2 infection. Each participant was administered an ad hoc questionnaire to document demographic, clinical, paraclinical, and anthropometric information.

Results

The adjusted seroprevalence of IgM and IgG were 28% and 100%, respectively. Serum IgM levels were higher in those with current infection (235.73 ± 109.42 IU/mL) compared to those with past infection (105.18 ± 16.09 IU/mL), subpatent infection (27.86 ± 9.68 IU/mL), and no infection (15.17 ± 1.83 IU/mL). The levels of IgM were the highest in those vaccinated with Oxford AstraZeneca (73.75 ± 32.48 IU/mL) or Pfizer BioNTech (74.95 ± 26.92 IU/mL) compared to those vaccinated with Sinopharm (37.69 ± 15.55 IU/mL) or Janssen (22.89 ± 4.95 IU/mL). The immune response was significantly modulated by gender, patient's age, presence of any comorbidity, and obesity. In Pfizer BioNTech-vaccinated, the levels of IgG were reduced in obese participants.

Conclusion

This study outlined a significant variation of immune response by type of vaccine, with the modulating effect of factors such as infection, demographical characteristics, and obesity.