Research Project on the Real Effectiveness and Impact of Vaccination Against Rotavirus Diarrhea in DR Congo

Vaccination is one of the most effective investments in public health. It contributes to the significant reduction of diseases and long-term disabilities [1]. Thus, several vaccines have been used for several decades in different countries. Their main expected impact is to significantly reduce mortality and morbidity due to the infectious diseases they target and thus save millions of human lives.

Although the proofs of efficacy of these different vaccines (Efficacy) have always been demonstrated during randomized controlled clinical trials under ideal conditions, thus allowing their approval or their marketing, many questions about the efficacy of the vaccine in the real conditions (Effectiveness) can only be given by observational approaches after the use of the vaccine [2]. This is because the results of randomized trials do not take into account certain real conditions of their use which may be either related to vaccines (vaccine storage conditions, observance of dosage, route of administration, number doses and intervals required between doses, etc.), or related to the host (age at the time of vaccination, genetic factors, immunosuppression, nutritional status, comorbidities, etc.) which can modify the immune response and vaccine efficacy in certain populations [3-5]. In addition, herd immunity is also not taken into account, which may lead to an underestimation of the overall effect of the vaccine in the population. This is why once large-scale vaccination has started, it is recommended to document its effectiveness in the field to determine the protection conferred by the vaccine in a population under real conditions of use “Effectiveness” [6,7].

A quick review of the literature on the real effectiveness of available vaccines against rotavirus diarrhea provides the following information. Overall, Rotarix and Rota Teq reduce the risk of hospitalization due to rotavirus-associated gastroenteritis by nearly 70% in fully immunized children, while Rotavac and Rotasiil show a moderate reduction in the risk of hospitalization due to gastroenteritis associated with rotavirus around 30% [8]. In Africa, vaccination with four vaccines currently prequalified by WHO (Rotarix, RotaTeq, Rotavac and RotaSiil) contributes to the reduction of approximately 40% of hospitalizations due to rotavirus-associated gastroenteritis in children under 5 years after the introduction of the vaccine for the period from 2006 to 2018 [9]. Considering some countries taken individually, we note for example that in Rwanda, a complete series of 3 doses was 75% effective against gastrointestinal -rotavirus enteritis requiring hospitalization or a visit to a health center in children and in Malawi, the estimated effective vaccine against rotavirus transmission was 39% [10,11].

In the Democratic Republic of Congo (DRC), the Expanded Vaccination Program (EPI) was set up in 1978 with the mission of contributing to better survival of the mother-child couple by reducing morbidity and mortality due to diseases Vaccine-preventable. The country introduced the rotavirus diarrhea vaccine “Rotasiil” in October 2019 [12,13]. It is important to note that the introduction of the Rotasiil vaccine was 10 years after the establishment of surveillance in Rotavirus gastroenteritis sentinel sites which revealed that 61% of diarrhea in children aged 0 to 5 years was caused by Rotavirus for data collected from August 2009 to June 2012 [14].

Although post-introduction vaccine impact and efficacy data for Rotavirus diarrhea vaccine (in monovalent and pentavalent vaccines) are available at the global level, at the level of the African region and for some African countries, but the Democratic Republic of Congo does not yet have these very useful data. However, the many challenges facing the vaccination system suggest that they would have an influence on the effectiveness of vaccines administered in the DRC: The EGEV shows that the score of the cold chain equipment temperature monitoring criterion does not is only 55% nationwide. The temperature readings and alarms are not subject to evaluation and analysis by the service providers and, consequently, there is no recording of these results nor any taking of corrective measures in a register. In addition, some nurses in health centers do not know the recommended temperature ranges for storing vaccines and do not know how to correctly fill in temperature sheets [15]. In terms of nutritional status, the DHS survey shows that among children under 6 months the proportion of children with growth retardation is 15% and that of those with the severe form of Chronic malnutrition is increasing and exceeds 7%, while 11% of children under 12 months suffer from acute malnutrition [16]. In addition to these two considerations, other situations, even if they are not precisely quantified, are not negligible in their possibilities of influencing vaccine efficacy, including: non-compliance with appointment intervals for taking vaccines represented by a considerable proportion of children recovered by community relays; the proportion of immunosuppression by HIV or other causes as well as ethnic diversity which may reflect genetic diversity.

This is why we wish, through this research project, to evaluate the real effectiveness (Effectiveness) and the impact of vaccination against Rotavirus diarrhea in order to assess the contribution of the vaccination program according to the mission assigned to it. assigned in the DRC.

This research project aims to answer these questions:

- What is the real level of effectiveness of the Rotasiil vaccine administered in the DR Congo?

- What are the factors explaining this level of real effectiveness of the Rotasiil vaccine administered in the D.R. Congo?

- What is the impact of vaccination on the disease and changes in epidemiology and circulating strains after the introduction of rotavirus vaccine in DR Congo?

In October 2019, the Democratic Republic of the Congo introduced the Rotasiil vaccine into the vaccination schedule for children aged 0 to 11 months given in i.e., 10 years after setting up sentinel site surveillance with the aim of contributing to reducing the burden of morbidity and mortality due to Rotavirus gastroenteritis. Carrying out this research project will allow the country, in addition to the general objectives of surveillance of rotavirus infection, to achieve the 2 specific objectives of this surveillance when à country has already introduced à rotavirus vaccine into the vaccination schedule. Which are: 1. To monitor the impact of vaccination on disease and changes in epidemiology and circulating strains following the introduction of rotavirus vaccine; 2. Assess the effectiveness of vaccines using surveillance as a platform for special studies [17]. This will make it possible to assess the contribution of the vaccination program according to the mission assigned to it and also help to strengthen the implementation of surveillance.

Goals

We set ourselves two objectives for the realization of this research:

First, to determine the real vaccine effectiveness (Effectiveness) after the introduction of Rotasiil in the vaccination schedule in force in the D.R. Congo.

Second, to determine the impact of vaccination against rotavirus diarrhea on the epidemiology of the disease and the viral epidemiology after its introduction in the D.R. Congo.

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