Seroprevalence of measles and rubella antibodies in vaccinated and unvaccinated infants in the Lao People’s Democratic Republic

Background Even though measles vaccination was introduced in the Lao PDR in 1984, coverage rates remain consistently low and outbreaks continue to occur frequently. This study was performed to investigate the seroprevalence of measles and rubella antibodies in vaccinated and unvaccinated children from Central Lao PDR. Methods Antibody titres of 1090 children aged 8–29 months who were vaccinated at different levels of the health care system were assessed by ELISA. Bivariate and multivariable analyses were performed to identify factors affecting seropositivity against measles and rubella. Results Among the vaccinated children, 67.5% in Vientiane Province and 76.4% in Bolikhamxay Province were double positive/borderline for measles and rubella IgG. A high proportion of unvaccinated children at both study sites (24.4% and 38.4%) were positive/borderline for measles and/or rubella. Time since vaccination <180 days, more than two siblings, and a mother who is a farmer/labourer were negatively associated with seropositivity. Conclusions A high prevalence of measles and rubella antibodies was found in unvaccinated children, indicating widespread circulation of both viruses and underreporting of cases. The high proportion of vaccinated children still susceptible to measles suggests problems with vaccine immunogenicity, emphasizing the need for regular evaluations of vaccine efficacy and management

Seroprotection at different levels of the healthcare system after routine vaccination with diphtheria-tetanus-pertussis whole cell--hepatitis B--haemophilus influenzae type B in Lao People’s Democratic Republic

Background The Lao People’s Democratic Republic continues to sustain a considerable burden of vaccine-preventable diseases because of incomplete vaccine coverage and weak vaccine responses. We have assessed seroconversion after routine vaccination with the pentavalent vaccine to capture weaknesses of vaccine management at the different levels of the healthcare system. Methods A total of 1151 children (aged 8–28 months) with 3 documented doses of the pentavalent vaccine delivered at central hospitals in Vientiane and the provincial hospital, 3 district hospitals, and 10 health centers in Bolikhamxay province were enrolled. Sociodemographic information was collected with a standardized questionnaire. Serum samples were analyzed for antibodies against vaccine components, and bivariate and multivariable analyses were performed to identify risk factors for low vaccine responses. Results Seroprotection rates at the provincial, district, and health center level were as high as in central hospitals, but seroprotection rates in areas covered by remote health centers were significantly lower. Protective levels also rapidly decreased with age at sampling. Seroprotection rates in Bolikhamxay against the different components reached 70%–77% and were up to 20% higher than in previous studies in the same region; 18.8% more children received the hepatitis B vaccine birth dose and the hepatitis B virus infection rate was 4 times lower. Conclusions Vaccine immunogenicity has dramatically improved in a central province, likely due to training and investment in the cold chain. Nevertheless, there remains a need to focus on the “last mile” in remote areas were most children are vaccinated through outreach activities

Seroprevalence and risk factors of hepatitis B and C virus infections in female workers of Lao garment factories

The prevalence of hepatitis B and C virus infections may be higher in vulnerable populations or in individuals likely to be exposed through risk behaviors such as female garment factory workers in Lao People’s Democratic Republic. A cross-sectional study was performed on 400 female garment workers in Vientiane Capital. Women were tested for hepatitis B virus surface antigen and antibodies against hepatitis B core, surface antigen and hepatitis C virus using commercial Enzyme-linked immuno-absorbent assays. Participants completed a standardized questionnaire about potential risk factors for both infections. Sixteen women (4±1.9%) were HBsAg carriers, 187 (47%) had anti-HBc, 116 (29%) anti-HBs and 7 (1.8±1.3%) anti-HCV antibodies. Three factors were significantly associated with the presence of anti-HBc (indicating previous exposure to HBV): (i) residence in dormitories, (ii) more than one sexual partner, (iii) history of abortion. Despite a high risk of exposure, the prevalence of anti HBV and anti HCV infection markers in this sample of female workers was not higher than in the Lao general population. Our data suggest that exposure to HBV happens later during life and was significantly associated with sexual risk behavior. Thus, this study highlights the vulnerability of these women who were mostly young, uneducated, unvaccinated, of rural origin and were not aware of the risk of infections. An occupational health program targeting the female factory workers should be implemented in Lao PDR

Unexpectedly high prevalence of hepatitis C virus infection, Southern Laos

During 2017–2019, a total of 88/753 (11.7%) of patients 5–90 years of age in hospitals in Saravan Province, Laos, were seropositive for hepatitis C virus antibodies. Viral RNA was found in 44 samples. Sequencing showed high diversity within genotype 6. We recommend exposure-risk investigations and targeted testing and treatment

Age-stratified seroprevalence of vaccine-preventable infectious disease in Saravan, Southern Lao People’s Democratic Republic

Background Lao People’s Democratic Republic has frequent outbreaks of vaccine-preventable diseases (VPD). This study aimed to determine susceptibility and exposure to VPD in Saravan, a rural province with high ethnic diversity and some of the poorest health indicators nationwide. Methods Patients from three district hospitals and one provincial hospital were enrolled. Serum was tested by ELISA for IgG against hepatitis B virus (HBV), tetanus, diphtheria, measles, and rubella. Results The study enrolled 2463 participants aged 5–90 years. Exposure to HBV was 33.2% and increased with age up to 62.4% of those aged >50 years. HBV surface antigen prevalence was 5.7% in males and 2.4% in females; 9.9% had serology compatible with vaccination. Seroprevalence of protective anti-tetanus antibodies was 46.3% overall. Protective anti-diphtheria seroprevalence was 40.5%. Anti-measles seroprevalence increased from 16.7% in those aged 5–10 years to 97.7% in those aged >50 years. Anti-rubella seroprevalence was 93.0% overall. There were differences in seroprevalences between sex, districts and ethnicity. Conclusions Routine infant vaccination needs strengthening in order to close the immunity gaps. High burden of HBV infection should be addressed by increasing birth dose vaccine coverage. Regional and ethnic differences need to be investigated to enable a targeted approach to vaccination

Hepatitis B virus in Lao dentists: a cross-sectional serological study

Introduction and objectives Hepatitis B virus (HBV) is endemic in Lao PDR, with up to 10% chronic infections in adults. Dentists have high risk of exposure and transmission to their patients. The aim was to investigate the serological profiles of vaccination, exposure and susceptibility to HBV. In addition, we determined the knowledge, attitude and practice (KAP) of Lao dentists toward HBV. Materials and methods Dentists and dental assistants were recruited from 186 private dental clinics in Vientiane Capital. They completed a KAP questionnaire and serum was tested by ELISA for HBV markers (anti-HB surface antigen, anti-core antigen, HBV surface antigen). Results 206 dentists and 111 dental workers aged between 18–63 years were included. Serology data showed that 37.8% had previous exposure (49.0% of males and 32.4% of females) and 5.0% were chronically infected (7.7% of males and 3.8% of females). Less than 15% had serological evidence of vaccination and 66.8% were unprotected against infection. Knowledge of HBV was mostly low, for example 61.8% were aware of the childhood HBV vaccine. Just over half said that they should give dental care to HBV carriers. About one quarter reported accidental blood exposure during the last 6 months but knowledge about procedures after exposure was low. Conclusions Lao dentists are at high risk of occupational exposure to HBV but have low awareness and serological protection. There is a need to introduce mandatory vaccination, to strengthen occupational health in health care providers and to further develop the academic curricula of dental students

Seroprevalence and risk factors of hepatitis B and C virus infections in female workers of Lao garment factories

<div><p>The prevalence of hepatitis B and C virus infections may be higher in vulnerable populations or in individuals likely to be exposed through risk behaviors such as female garment factory workers in Lao People’s Democratic Republic. A cross-sectional study was performed on 400 female garment workers in Vientiane Capital. Women were tested for hepatitis B virus surface antigen and antibodies against hepatitis B core, surface antigen and hepatitis C virus using commercial Enzyme-linked immuno-absorbent assays. Participants completed a standardized questionnaire about potential risk factors for both infections. Sixteen women (4±1.9%) were HBsAg carriers, 187 (47%) had anti-HBc, 116 (29%) anti-HBs and 7 (1.8±1.3%) anti-HCV antibodies. Three factors were significantly associated with the presence of anti-HBc (indicating previous exposure to HBV): (i) residence in dormitories, (ii) more than one sexual partner, (iii) history of abortion. Despite a high risk of exposure, the prevalence of anti HBV and anti HCV infection markers in this sample of female workers was not higher than in the Lao general population. Our data suggest that exposure to HBV happens later during life and was significantly associated with sexual risk behavior. Thus, this study highlights the vulnerability of these women who were mostly young, uneducated, unvaccinated, of rural origin and were not aware of the risk of infections. An occupational health program targeting the female factory workers should be implemented in Lao PDR.</p></div

Hepatitis B virus in Lao dentists: A cross-sectional serological study

Introduction and objectives: Hepatitis B virus (HBV) is endemic in Lao PDR, with up to 10% chronic infections in adults. Dentists have high risk of exposure and transmission to their patients. The aim was to investigate the serological profiles of vaccination, exposure and susceptibility to HBV. In addition, we determined the knowledge, attitude and practice (KAP) of Lao dentists toward HBV. Materials and methods: Dentists and dental assistants were recruited from 186 private dental clinics in Vientiane Capital. They completed a KAP questionnaire and serum was tested by ELISA for HBV markers (anti-HB surface antigen, anti-core antigen, HBV surface antigen). Results: 206 dentists and 111 dental workers aged between 18–63 years were included. Serology data showed that 37.8% had previous exposure (49.0% of males and 32.4% of females) and 5.0% were chronically infected (7.7% of males and 3.8% of females). Less than 15% had serological evidence of vaccination and 66.8% were unprotected against infection. Knowledge of HBV was mostly low, for example 61.8% were aware of the childhood HBV vaccine. Just over half said that they should give dental care to HBV carriers. About one quarter reported accidental blood exposure during the last 6 months but knowledge about procedures after exposure was low. Conclusions: Lao dentists are at high risk of occupational exposure to HBV but have low awareness and serological protection. There is a need to introduce mandatory vaccination, to strengthen occupational health in health care providers and to further develop the academic curricula of dental students

Association between socio-demographic characteristics, knowledge and risk factors with Anti-HBc.

<p>Ref = reference.</p