Lay summary for the research article published under the DOI: 10.1016/j.vaccine.2020.05.057
Maternal immunity and seasonality play an important role in how low-income countries such as Ghana can stem the spread and deaths of rotavirus with vaccines. These vaccines have a much lower effectiveness in low-income countries and now researchers have started to piece together the reasons behind this vaccine weakening.
Rotavirus-associated gastroenteritis (RVGE) is a viral disease that causes diarrhoea. It killed 528 000 children globally in 2000. Since then, Ghana introduced the Rotarix vaccine in 2012, which reduced the deaths of children under 5 years old.
However, while the world saw a sharp decrease in deaths from rotavirus, in 2013 sub-Saharan Africa still had more than half of the 215 000 global deaths.
This study set out to find what caused the rotavirus vaccine to be much less effective in Ghana, as an example of a low-income country. They wanted to find the factors that can be dealt with so that governments can formulate strategies to improve the performance of the rotavirus vaccine in Ghana.
The researchers gathered data regarding rotavirus cases and deaths from three hospitals in Ghana: Korle-Bu Teaching Hospital in Accra, Komfo Anokye Teaching Hospital in Kumasi, and War Memorial Hospital in Navrongo. They then used mathematical models to compare what happened before and after the rotavirus vaccine was introduced, and investigated the factors that might have contributed to the low vaccine effectiveness.
The study showed that Accra had the highest rate of rotavirus infections, while the Navrongo region had the lowest rotavirus transmission rates. The researchers suspected that the immunity children get from their breastfeeding mothers against rotavirus might interfere with the vaccine; they found that maternal immunity was five (5) months in Accra, while it was a shorter three (3) months in Navrongo.
They found that the vaccine was most effective in Accra and Kumasi, and least effective in Navrongo.
While similar studies have used mathematical models to evaluate the effects of vaccines on rotavirus in low income countries, they considered how rotavirus is transmitted and spread within a country. These other studies have found that the rotavirus vaccine’s effectiveness can be greatly weakened when patients do not receive the complete vaccine shots in a schedule of multiple doses.
The researchers have added to this body of knowledge by considering the duration of maternal immunity for specific regions within Ghana.
The study was able to gather data from before and after vaccines were introduced but the hospital in Navrongo did not have data for a period spanning a year and a half. This is problematic as it may compromise their results for the Navrongo region.
The results of the study highlight the need to further explore the relationship between rotavirus seasonality, maternal immunity duration, and vaccine response rate in terms of how they impact vaccine effectiveness. With such information, governments in sub-Saharan Africa can develop strategies that improve vaccine impact in places with high seasonal rotavirus transmission.
Number of words: 430 words
Rotavirus incidence remains relatively high in low-income countries (LICs) compared to high-income countries (HICs) after vaccine introduction. Ghana introduced monovalent rotavirus vaccine in April 2012 and despite the high coverage, vaccine performance has been modest compared to developed countries. The predictors of low vaccine effectiveness in LICs are poorly understood, and the drivers of subnational heterogeneity in rotavirus vaccine impact are unknown.
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