Prevalence of Children Vaccinated against Viral Hepatitis B in Brazzaville ()
1. Introduction
Viral hepatitis B (VHB) is an inflammation of the liver parenchyma caused by an attack by the VHB virus present in the physiological fluids of the infected individual [1] . It is a major public health problem. The World Health Organisation (WHO) estimates the global prevalence of HBV at 3.5%, and it is responsible for around 88,720 deaths from serious complications such as cirrhosis and liver cancer [2] [3] [4] [5] . Sub-Saharan Africa is a highly endemic region, with a prevalence of over 8%. Vertical transmission is the main mode of contamination [6] , and remains a major source of chronic liver disease when infected children reach adulthood, with a high morbidity and mortality rate [7] [8] [9] . In the Congo, the prevalence of hepatitis B in the general population is 12.5%, spread over 7 of the country’s 12 departments. According to individual studies, these prevalences vary between 5% and 15% from one population to another [10] ; however, the prevalence in children is not known. Management of chronic and complicated forms of the disease is difficult and costly. Eradication through a systematic vaccination policy, adopted in several countries, remains the best option, as vaccines are the main means of protection against the HVB virus [8] . According to the WHO, developing countries have not yet achieved high levels of vaccination coverage, despite systematic, free vaccination and the introduction of the birth dose [11] [12] [13] . In the Congo, the HVB vaccine was introduced into the immunisation schedule by the Expanded Programme on Immunisation (EPI) in 2009 [14] , and sine the no évaluation has been carrier out in the infant population, henné the intérêts of this first study, the aim of which was to determine the prevalence of children vaccinated against HVB in Brazzaville, to identify the vaccines use for vaccination and to investigateur the causes of incomplete vaccination of children (see the Appendix).
2. Patients and Methods
This was a cross-sectional, analytical study conducted from January to September 2019 (i.e. naine months), in naine health centres selecte from the naine health districts of the Brazzaville department. The general population was represented by all children except for vaccination in the health centres hère vaccination was carrier out on a fixe basis during the study period. The study population consisted of children aged six months to six years except to be vaccinated in the aforementioned health centres during the study period. We included children aged six months to six years who were supposed to have received the primary vaccination and whose parents consented to participate in the study after signing the informed consent form on a voluntary basis. Children who did not have a postnatal follow-up form and/or vaccination record and those whose parents had not consented to the study were not included. We excluded all children who came for their first vaccination. Sampling was simple random using the Random method. We carrier out a three-stage survey using the same method: the first stage involved identifying the health districts in the Brazzaville département, the second stage involved selecting the vaccination centres within the health districts to ensure that they were representative; this resulted in the selection of naine representative health centres. At the third level, children were selecte for each vaccination centre on the basis of registers of appointments for children due to be vaccinated. Data collection was carrier out by the same interviewers (a PhD student and a nurse). The interviews were conducted in French and the national languages. A pre-established questionnaire was use to collect information on the vaccination schedule, based on interviews with the mothers, analysis of vaccination records and postnatal follow-up forms. The variables studied were socio-demographic (sex, age, level of education, place of residence, parents’ level of education and occupation, parents’ marital status), those relating to vaccination (type of vaccine, number of doses, compliance with medical appointments and/or compliance with the interval between doses, booster doses according to age) and variables relating to parents’ knowledge of HBV and vaccination. We considered as vaccinated any child who had received a primary vaccination (the 3 recommended doses of vaccine against HBV). A child was correctly vaccinated when he or she had received the primary vaccination with a one-month interval between doses and the booster vaccination(s); otherwise, the vaccination was said to be incomplete. The combined vaccine contains several viral antigens and is administered to infants in combination with other vaccines, such as the pentavalent vaccine (combining the diphtheria, tetanus, pertussis or DTP, Haemophilus influenzae type b and HVB vaccines), which is the recombinant vaccine use in the Congo’s EPI. The monovalent vaccine contains only the HBs antigen and is administered alone from birth. Vaccination was said to be mixed when the same child received both the monovalent vaccine at birth and the pentavalent later on. The degree of protection of children against HBV was good when it was greater than 96%. Statistical analysis was performed using Microsoft Excel R.2.10.1. Quantitative variables were expressed as mean and standard deviation, and qualitative variables as frequency and proportion. The Pearson Chi-square test was use to compare the variables. Differences were considered statistically significant when the P < 0.05 value was reached. This work carrier out for the thesis with a view to obtaining a doctorate in medicine had been required a favourable opinion from the Health Sciences Research Ethics Committee of the Congo (No. 018/MRST/IRSSA/CERSSA).
3. Results
The overall prevalence of children vaccinated against HBV in Brazzaville was 96.2% (180/187). Vaccination prevalence by health district is shown in Figure 1. Of the 187 children included, 106 were boys (56.1%) for 81 girls, giving a sex ratio of 1.3. The mean age of the children was 23.38 months ± 2.77 (extremes: 6 months to 6 years). The under-24-month age group was the most représente, with 58.2% (n = 109). 83.9% (n = 157) of the children did not attend school and were looked after at home by their mothers, 14.9% (n = 28) attended pre-school and 1% (n = 2) attended primary school. Of these, 55.6% (n = 104) were from parents with secondary education, 29.4% (n = 55) with higher education, and 14.9% (n = 28) with primary education or no education at all. One hundred and fifty children (80.2%) came from married parents and 19.7% (n = 37) from single mothers. In terms of vaccination practices, 86% (n = 161) of parents had respected medical appointments, and for these children, the free interval between vaccine doses was respected. One hundred and seventy-six children were vaccinated exclusively with the combined vaccine (pentavalent) from the age of 2 months, i.e. a prevalence of 97.7%, and 2.2% (n = 4) of children had received the mixed vaccination. The distribution of vaccinated children according to the number of doses of vaccine received is shown in Figure 2. 87.7% (n = 158) of children had not received a booster vaccination. The incompletely vaccinated children lived in the Talangai health district in the Mikalou (71%) and Ngamakosso (14.7%) neighbourhoods, and in the Moungali health district in the Plateaux des 15 ans neighbourhood (14.3%). The reasons for incomplete vaccination were related to the parents and are shown in Table 1.
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Figure 1. Distribution of the prevalence of children vaccinated against HBV by health district.
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Figure 2. Breakdown of children by number of doses of HBV vaccine received.
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Table 1. Reasons for incomplete vaccination linked to parents.
4. Discussion
We report the results of a study on the prevalence of children vaccinated against HBV in Brazzaville [15] . The study was self-financed, which meant that it could not be carrier out in all 12 of the country’s departments because of financial difficulties. The monovalent vaccine is systematically recommended by the WHO from birth within 72 hours of delivery for better efficacy, which justifies modifying the EPI vaccination schedule in line with this recommendation. However, it should be emphasised that in practice this change is not yet effective due to the non-availability of the monovalent vaccine in the Congolese EPI, which reduces the number of children fully vaccinated.
The overall prevalence of children vaccinated in Brazzaville was satisfactory (96.2%). Prevalence varied significantly from one arrondissement to another (p < 0.05). Talangai had a lower vaccine prevalence (79%) than the other health districts, because it was one of the most densely populated health districts at the time of the study. However, WHO-CONGO reported in 2018 that HBV vaccination coverage was lower in Madibou (74%) and Makélékélé (50.7%), higher in Moungali (86.9%), Poto-Poto (83.8%), Ouenzé (81.3%) and Talangai (81.6%), and higher in Djiri (99%) and Mfilou (93.3%) [16] . This difference can be explained by the fact that in the present study it was a question of the prevalence of vaccinated children, the denominator not being the same in relation to the immunisation coverage studied by the WHO. Variability in the prevalence of HBV vaccination has also been observed by Personne V et al, in France [17] . The same applies to the predominance of males, although the same author found no statistically significant difference (p = 0.06). This is probably a coincidence, perhaps related to the type of sampling. The predominance of children under 24 months of age has also been reported in France (18 to 23 months), probably because of methodological similarities in the choice of the age range of their study population. In our case, it is also due to the fact that EPI vaccination is free (up to 18 months), which increases mothers’ acceptance of these infants. In our series, the majority of children were vaccinated with pentavalent vaccine (the only HVB vaccine available in the EPI), and 97.7% received primary vaccination. Monovalent vaccine was use at birth in only 2.23% of children because it was not available in the EPI. The few children who were vaccinated were prescribed by the paediatrician at the parents’ expense. The constant use of combined vaccines for children under one year of age in national immunisation programmes is also the case in many African countries, and even in France [14] [18] [19] [20] , because of the free and compulsory nature of these vaccines. Vaccination uptake varied according to place of residence. The majority of children with incomplete vaccination lived in the Talangai (85.7%) and Moungali (14.3%) health districts. This result can be explained by the fact that the children’s parents had no knowledge of the disease itself, or of the existence of preventive measures against it, in particular vaccination against HVB. The national programme to combat the newly-created viral hepatitis centre will need to be operational in order to carry out public awareness campaigns using targeted communication on HVB to change behaviour, and to put in place an effective national vaccination policy to reach all vulnerable populations, particularly pregnant women, newborns, infants and young children.
5. Conclusion
Although the prevalence of children vaccinated against HVB is high in Brazzaville, it is still insufficient in the Talangai and Moungali health districts, due to parents’ ignorance of the disease and vaccination. Almost all children are vaccinated with pentavalent because monovalent is unavailable in the Congolese EPI. Prevention is therefore the most effective weapon, and this involves making the monovalent vaccine available from birth, adhering to the vaccination schedule and educating the population to change their behavior.
Appendix: Prevalence of Children Vaccinated against Viral Hepatitis B in Brazzaville
Survey sheet no. ----- survey date: -----/ __ /------
1) Identification of respondent and epidemiological parameters
Arrondissement -----------------------
Neighbourhood
CSI
Child’s number
Sex male / / female / /
Age (months) -------------------
Birth rank---------------------------------------
Number of pre-school children in sibling group-------------
Child’s guardian ------------------------
How is the child looked after: 1. nursery / / 2. nanny / / 3. home / /
Father’s occupation ----------------
Mother’s occupation------------------
Parents’ level of education :
Mother: 1. primary / / 2. secondary / / 3. higher / / 4. None
Father: 1. primary / / 2. secondary / / 3. higher / / 4. None
Parents’ marital status: 1. single / / 2. married / / 3. living as a couple / / 4. none
Parents’ practical knowledge of vaccination against EPI diseases: yes / / no/ /
Particularly hepatitis B: yes / / no / /
2) Parameters relating to vaccination
Has the child already been vaccinated? If not, why not?
a) Yes / / go to 2
b) No
-no reason / /
booklet lost / / -child never vaccinated / /
-child never vaccinated / /
Can you show the vaccination record? Has the child been vaccinated against hepatitis B?
a) Yes / /
b) No / /
Type of vaccine: 1. Combined vaccine (EPI) /___ / or 2. Monovalent vaccine /____ /
a) Monovalent: from birth 1. yes /___ / 2. no /___ / when ?and specify number of doses -----------------------------------------------------------------------
b) Pentavalent, at least 3 doses: at 2 months /__ / at 3 months /__ / at 4 months /__ /
c) Booster yes / / when----------- ? No / / when------------ ?
Post-vaccination reactions: 1. Fever 2. Pain 3. rash 4. None -- /__ / --- 5. other------------
Time between first and second dose ---------------------------
Time between second and third vaccination dose--------------------------------
3) Parameters relating to parental consent: From a medical point of view, what are the arguments in favour of vaccination against hepatitis B?
a) It is a vaccine that prevents the fatal risk of hepatitis B: 1 = Yes /__ /; 2 = No /__ /
b) This vaccine has been shown to be safe in infants: 1 = Yes /__ /; 2 = No /__ /
c) Vaccination against hepatitis B before the age of 12 provides immunity for several decades: 1 = Yes /__ /; 2 = No /__ /
d) The benefit/risk balance of the hepatitis B vaccine is largely in favour of vaccination: 1 = Yes /__ /; 2 = No /__ /
4) Biological parameters :
HBsAg: 1. positive; 2. negative /__ /
Anti-HBs AC level: 1 = 10 IU/L; 2 = greater than 10 IU/L; 3= 50 IU/L /___ /