Hepatitis A and B Immunity in South Africa. Who Should Be Vaccinated?
Travel Doctor Corporate, Johannesburg, South Africa,
Travel Doctor, Johannesburg, South Africa
University of the Witwatersrand, Johannesburg, South Africa,
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To determine the need for Hepatitis A and B vaccination in travellers to and from South Africa.
Our clinic provides comprehensive corporate travel health risk management in Johannesburg, South Africa. The bulk of our clients travel for work.
Several studies conducted in South Africa over the last 20 years indicate that incidence of Hepatitis A is decreasing and since the inclusion of Hepatitis B in the EPI in 1995 incidence rates of Hepatitis B have been decreasing.
The aim of our study was to determine the need and cost effectiveness of vaccination against Hepatitis A and B in our cohort of travellers that travel out of South Africa for work. In addition it provides a snapshot of the need for vaccination in travellers coming to South Africa.
We collected retrospective data for Hepatitis A and B immunity in our clinic. Our cohort consisted mostly of candidate seafarers and mine workers. We reviewed clinical records from January 2019 to December 2022. We documented demographic data as well as HAIgG and HAIgM, HBsAb and HBsAg.
These tests form part of routine “pre-deployment medicals”. We compared the results against national incidence rates.
We reviewed 210 patient records, of which 82 candidates were tested for Hepatitis A immunity and 162 candidates were tested for Hepatitis B immunity.
Out of the 82 candidates tested for Hepatitis A IgG, 59% were found to be immune either through natural immunity or prior immunization.
This compares to a seroprevalence rate of 88% positivity for IgG in a study conducted by the NICD on the general population of all ages.
Out of the 162 candidates tested for Hepatitis B surface antibody, 41% were found to be immune. This does not distinguish between natural and vaccine acquired immunity.
The national statistics for Hepatitis B immunity were higher, but it’s important to note that the age group tested for the national study was younger than 25 years, whereas the average age of our cohort was 36 years.
Only 7 of the 22 candidates who were young enough to have been vaccinated (EPI) showed HBsAb immunity.
Our cohort consisted mostly of expatriate travelers for work. The long-term traveler to Africa may have a higher risk profile and require expert guidance including counselling on risk and exhaustive vaccination. Hepatitis A and B are both preventable by vaccination as discussed below and the need for vaccination is important in both travelers out of South Africa and those who may want to visit our country from abroad.
Hepatitis A is typically spread through contaminated food and water, and it is most common in areas with poor sanitation. In South Africa, the prevalence of Hepatitis A has decreased significantly in recent years due to improvements in sanitation and hygiene transitioning from high to intermediate endemicity. However, there are still high-risk populations, such as young children, healthcare workers, individuals living in crowded conditions, and importantly non-immune adults who should be vaccinated. According to a study conducted in Johannesburg, only 17% of children aged 2 to 5 years had evidence of prior Hepatitis A infection, indicating that a significant proportion of the population remains vulnerable to the disease.
A 2021 study conducted in Pretoria, South Africa showed HAV seroprevalence by 10 years of age only 68.6%, and > 90% seropositivity only reached beyond 15 years of age. Similarly, a study conducted in 2019 showed 44% seroprevalence in the 1 – 7 year age group with >90% being reached after the age of 10 years. This study included surveillance data that showed that a substantial number of symptomatic hepatitis A infections occurred in the 7 – 40-year age group.
The intermediate prevalence of total anti-HAV among children and adolescents in South Africa suggests the country’s improvement of safe water and food supply, hygiene, and sanitation. However, it leaves older children and adults vulnerable to acute HAV infection, and there is a potential for outbreaks such as the 1988 Hepatitis A outbreak in Shanghai where a group of young adults who had grown up under good sanitation conditions contracted the disease resulting in 320 000 cases and 47 deaths. This emphasises the need for rigorous health promotion and adult vaccination.
Hepatitis B is spread through contact with infected bodily fluids, such as blood or semen. In South Africa, the prevalence of Hepatitis B is high, with an estimated 7.6% of the population being chronically infected. The introduction of the Hepatitis B vaccine in the country’s Expanded Program on Immunization (EPI) has helped to reduce the incidence of the disease. However concerning data collected in Cape Town 10 years after the introduction of the EPI programe showed 40% of children supposedly vaccinated had no evidence of immunity and some even showed evidence of prior infection. The conclusion of this study lead to the consideration of offering booster vaccination to the population as a whole.
Instead of looking to seroprevalence as a marker for immunity a study conducted in Taiwan looked at the number of HBsAg-positive individuals between 1984 and 2004 since the introductive of Hepatitis B vaccination. HBsAg-positive individuals younger than 20 years decreased from 9.8% to 0.6%. There was also an associated drop in HBV-related complications.
Closer to home, a retrospective quantitative cross-sectional study on routine HBV laboratory data obtained from the NHLS on laboratory-diagnosed HBV infection in the public health sector at a national level showed there was a decline in the national incidence rate of acute HBV infection per 100,000 population over the years. This indicates some effectiveness of the Hepatitis B vaccination campaign.
As noted above, the argument remains that presence of detectable levels of Hepatitis B antibodies does not correlate with clinical immunity and should not be relied on solely.
In a 2020 study conducted in the US immunity to hepatitis B was defined by a positive anti-HBs test result (anti-HBs titer >10 IU/L from 1999 to 2006 and ≥12 IU/L from 2007 to 2016). However a better way to gather national data may be to look at Hepatitis B surface antigen positive cases (active infection) rather.
According to the World Health Organization guideline for HBV vaccination, there is no evidence to recommend a booster dose to those who completed the vaccine series and have a low risk of infection. However, it is recommended that people at high risk of infection receive a booster dose if their anti-HBs level is less than 10 mIU/mL.
In addition to the above, our group was relatively small, and we were unable to distinguish between natural immunity and previous vaccination.
We noted a lower prevalence in immunity against both Hepatitis A and B in our sample group than in three similar South African studies. It supports the notion that
- South Africa has moved from a high to intermediate endemicity for Hepatitis A leaving older non-immune age groups vulnerable to outbreaks of the disease
- Although Hepatitis B is included in the EPI there are still significant numbers of young adults who show no immunity to the disease
- Immunity in outbound travelers cannot be assumed
- Non-immune South Africans and travelers to South Africa are at risk and should be vaccinated
Hepatitis A and B continue to be significant public health concerns in South Africa, and vaccination is a key strategy for preventing the spread of these diseases. While progress has been made in reducing the incidence of both infections, there are still populations at high risk. Travelers to South Africa should be vaccinated against Hepatitis A and B.
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