# The effectiveness of COVID-19 Heterologous Vaccination: the experience from a Regional Hospital in Cameroon

## TL;DR

This study examines the effectiveness of mixing different types of COVID-19 vaccines in Cameroon, finding no significant difference in disease severity compared to using the same vaccine for both doses.

## Contribution

The study provides empirical evidence on the effects of heterologous vaccination in a low-resource setting with limited prior data.

## Key findings

- Fully vaccinated individuals had lower odds of severe disease (p=0.037).
- Heterologous vaccination showed no significant difference in morbidity compared to homologous vaccination (p=0.729).
- None of the patients who died were fully vaccinated.

## Abstract

With most COVID-19 vaccines requiring at least 2 doses, heterologous vaccination will facilitate vaccination programs where vaccine supplies fluctuate. However, with insufficient data on effects of heterologous vaccination in our setting, people remain reluctant to mix.

We seek to assess the effects of heterologous vaccination on morbidity and mortality.

This was a 7 months retrospective study for COVID-19 patients managed by the Bamenda Regional Hospital, Cameroon, running from the 18th August 2021 to 28th February 2022. Logistic regression used to asses relationship between predictors and outcome.

Our 1254 participants had a mean age of 50.1(±19.6) years, we had 24 (1.9%) being fully vaccinated, where 7 (29.2%) took heterologous vaccines. Also, 721 (57.5%) had the moderate/severe form of the disease. Those fully vaccinated had lower odds of having severe disease (p=0.037). However, heterologous vaccination compared to homologous vaccination had no significant difference on morbidity (p=0.729). Among patients who died, none was fully vaccinated.

The protective effect of vaccination on morbidity was similar in those with heterologous vaccination as well as those who took