Freeze-dried Live Attenuated Hepatitis A Vaccine >6.5LgCCID50
Overview
Freeze‑dried Live Attenuated Hepatitis A Vaccine is a preventive vaccine formulation containing a live attenuated strain of the hepatitis A virus with an antigen content of at least 6.5 log CCID50 per 0.5 millilitre dose, designed to stimulate protective immune responses against hepatitis A infection. The vaccine uses an attenuated H2 viral strain cultivated in human diploid cell substrates and then lyophilized (freeze‑dried) to enhance stability and shelf life. Upon reconstitution, the vaccine is administered by subcutaneous injection, typically in the upper arm for adults or anterolateral thigh for young children, to provoke an immune response that induces durable antibody production. Because it contains a live but weakened virus, the vaccine mimics natural infection without causing clinical disease, leading to long‑term immunity with one or two doses. It is indicated for active immunization against hepatitis A virus, which is primarily transmitted through contaminated food and water and can cause acute liver inflammation and systemic symptoms.
Background and Date of Approval
Live attenuated hepatitis A vaccines in freeze‑dried form have been developed and licensed in several countries, particularly where hepatitis A is endemic, to provide long‑lasting protection against hepatitis A virus infection. Freeze‑dried formulations emerged to replace unstable liquid preparations and extend shelf life while retaining antigenicity and immunogenicity. Freeze‑dried live attenuated hepatitis A vaccines, including those with the H2 strain and similar live viral backbones, have been approved for active immunization in individuals aged 12 months and older based on clinical evidence demonstrating immunogenicity and safety. Regulatory authorisation usually follows evaluation of potency (such as antigen content ≥ 6.5 LgCCID50), safety in target populations, and stability of the freeze‑dried product, ensuring suitability for routine immunization programmes.
Uses
The primary indication for Freeze‑dried Live Attenuated Hepatitis A Vaccine is active immunization to prevent hepatitis A infection in individuals aged one year and older, including children, adolescents, adults, and at‑risk groups such as travellers to endemic regions, healthcare and sanitation workers, and those with chronic liver disease. The vaccine is not intended for the treatment of established hepatitis A infection but for prophylaxis before exposure. Catch‑up immunization and administration in outbreak settings may be recommended depending on local public health policies.
Administration
The vaccine is administered by subcutaneous injection after reconstitution of the freeze‑dried powder with a sterile diluent. A typical schedule involves a single 0.5 millilitre dose for primary immunization, with some regimens recommending a second dose 6 to 12 months later to enhance long‑term immunity. Infants should be at least 12 months of age at the time of vaccination. Injection site and systemic responses should be monitored immediately following administration, and standard precautions observed.
Side Effects
Common side effects of Freeze‑dried Live Attenuated Hepatitis A Vaccine include pain, redness, or swelling at the injection site, mild fever, fatigue, loss of appetite, headache, irritability, drowsiness, and gastrointestinal discomfort such as nausea. These reactions are usually mild to moderate in intensity, transient, and resolve without intervention within a few days. Irritability and transient decrease in appetite are more commonly observed in paediatric populations.
Warnings
Serious adverse events following vaccination are rare but may include severe allergic reactions such as anaphylaxis. Individuals with known hypersensitivity to any component of the vaccine, including gelatin, trehalose, dextran, mannitol, or other excipients, should not receive the vaccine. Vaccination should be deferred in individuals with moderate or severe acute illness until recovery. As a live attenuated vaccine, its use in severely immunocompromised individuals warrants careful risk‑benefit assessment, and immune responses may be diminished.
Precautions
Before vaccination, healthcare providers should assess for history of severe allergic reactions to components of the vaccine or prior vaccination. There are no significant drug interactions that typically contraindicate vaccination, but timing relative to immunosuppressive therapies or immune globulin administration may influence immune responses. Live attenuated vaccines should generally be spaced from immunoglobulin products when possible to minimise interference with vaccine efficacy. Routine observation after vaccination helps identify any immediate hypersensitivity.
Expert Tips
Prescribers should confirm the indication for hepatitis A vaccination based on age, epidemiologic risk, and immunization history. Counsel caregivers and patients on the benefits of vaccination, potential side effects, and the importance of completing recommended doses for long‑term protection. Administer the vaccine via proper subcutaneous technique and monitor recipients briefly for acute reactions. Storage of the frozen freeze‑dried vaccine must be maintained within recommended temperatures to preserve potency, and reconstituted doses should be used promptly.