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[Horizontal transmission of live attenuated hepatitis A vaccine virus]
1Institute of Medical Biology, Chinese Academy of Medical Sciences and Peking Union Medical College, Kunming 650118, China.
Insights
The live attenuated hepatitis A vaccine (H2 strain) is safe and effective, showing good immunogenicity and minimal risk of horizontal transmission. While the vaccine virus can propagate, it maintains attenuated characteristics, preventing hepatitis A in the community.
Area of Science:
- Virology
- Immunology
- Vaccinology
Context:
- Hepatitis A remains a public health concern, necessitating effective vaccination strategies.
- Live attenuated vaccines offer a promising approach for infectious disease prevention.
- Understanding vaccine virus transmission is crucial for public health policy.
Purpose:
- To evaluate the horizontal transmission potential of a live attenuated hepatitis A vaccine (H2 strain).
- To assess the safety and immunogenicity of the H2 strain in children.
- To determine the virulence of the vaccine virus in a non-human primate model.
Summary:
- A study involving 199 children demonstrated high seroconversion rates (97.6%) in the vaccine group and lower rates (13.7%) in the contact group.
- Fecal shedding of the hepatitis A virus (HAV) was detected in both groups, indicating potential for horizontal transmission.
- Marmoset studies confirmed the attenuated nature of the vaccine virus, showing no adverse effects or significant liver damage.
Impact:
- The H2 strain exhibits good safety and immunogenicity, supporting its use in hepatitis A prevention.
- The vaccine virus propagates effectively while retaining attenuated properties, minimizing the risk of inducing hepatitis A.
- Findings suggest that while horizontal transmission may occur, it does not lead to disease in the vaccinated population or contacts.
Objective:
To investigate the horizontal transmission of virus after inoculation with live attenuated hepatitis A vaccine.
Methods:
One hundred and ninety nine children aged 4 approximately 7 years without anti-HAV and with normal ALT level have been screened out at two trial fields in Anning, Kunming and divided into vaccine group (82 children) and contact group (117 children) to observe the horizontal transmission of the live attenuated hepatitis A vaccine virus (H2 strain). Four supernatant specimens of HAV positive fecal suspension derived from individual vaccines and contacts were taken and injected intravenousely into 8 common marmoset (Callithrix jacchus) for detecting the virulence level of HAV.
Results:
The rates of seroconversion were 97.6% (80/82) for vaccine group 6 weeks after inoculation and 13.7% (16/117) for contact group at the ninth week of observation. The detection rates of fecal HAV were 89.5% (34/38) and 70.7% (53/75), respectively. No liver functional abnormality has been found in either groups. The responses of 8 marmosets separately infected with fecal shedding HAV of 2 vaccines and 2 contacts have been examined with neither elevations of serum liver enzyme nor liver histopathological changes but delay seroconversions as well as low titers of anti-HAV.
Conclusion:
The safety and immunogenicity live attenuated hepatitis A vaccine (H2 strain) were good. The vaccine virus could actively propagate but keep the stability of attenuated characteristics in human bodies, and might result in horizontal transmission but not induce hepatitis A in crowd.