Hepatitis virus (HAV) is a Picornavirus. It is non-enveloped and contains a single-stranded RNA packaged in a protein shell. There is only one type of the virus. HAV causes Hepatitis A (formerly known as infectious hepatitis), an acute infectious disease of the liver. This disease is most commonly transmitted by the fecal-oral route via contaminated food or drinking water. HAV infects approximately 10 million people every year worldwide, esp. in developing countries. The incubation period is 15-50 days, and mortality is less than 0.5%. Hepatitis A infection causes no clinical signs and symptoms in over 90% of infected children. Hepatitis A does not have a chronic stage and does not cause permanent liver damage. Following infection, the immune system makes antibodies against the hepatitis A virus that confer immunity against future infection (Wiki: Hepatitis A).
4. Microbial Pathogenesis
The virus spreads by the fecal-oral route, and infections often occur in conditions of poor sanitation and overcrowding. HAV enters the bloodstream through the epithelium of the oropharynx or intestine. Once HAV comes to the liver through the blood, it lives and multiplies within hepatocytes and Kupffer cells (i.e., liver macrophages). There is no apparent virus-mediated cytotoxicity, and liver pathology is likely immune-mediated. Virions are secreted into the bile and released in stool. HAV is excreted in large quantities ~11 days prior to appearance of symptoms or anti-HAV IgM antibodies in the blood (Wiki: Hepatitis A).
5. Host Protective Immunity
Following infection, the immune system makes antibodies against the hepatitis A virus that confer immunity against future infection (Wiki: Hepatitis A).
II. Vaccine Related Pathogen Genes
1. HAVgp2
Gene Name :
HAVgp2
Sequence Strain (Species/Organism) :
Hepatovirus A
Molecule Role Annotation :
A recombinant vaccinia virus containing most of the P1 region of hepatitis A virus (HAV) was constructed bearing epitopes from structural polypeptides VP4, -3 and -2, and the N terminus of VP. Inoculation of tamarin monkeys with the recombinant virus resulted in the development of a specific anti-HAV immune response which was protective against challenge with a virulent strain of HAV (Karayiannis et al., 1991).
HAVRIX (Hepatitis A Vaccine) is a sterile suspension of inactivated virus for intramuscular administration. The virus (strain HM175) is propagated in MRC-5 human diploid cells. After removal of the cell culture medium, the cells are lysed to form a suspension. This suspension is purified through ultrafiltration and gel permeation chromatography procedures. Treatment of this lysate with formalin ensures viral inactivation. Viral antigen activity is detected by ELISA and expressed in terms of ELISA Units (EL.U.) (FDA: Havrix).
n. Immunization Route
Intramuscular injection (i.m.)
o. Storage
Store refrigerated between 2° and 8°C (36° and 46°F) (FDA: Havrix).
HAVRIX can cause a severe allergic reaction (e.g., anaphylaxis) after a previous dose of any hepatitis A-containing vaccine, or to any component of HAVRIX, including neomycin. Hepatitis A vaccine may not prevent hepatitis A infection in individuals who have an unrecognized hepatitis A infection at the time of vaccination (FDA: Havrix).
r. Description
Indication: To support lowering the age indication for Havrix from two years to 12 months of age (FDA: Havrix).
s.
Human Response
Vaccination Protocol:
A double-blind, randomized controlled study was conducted in school children (age 1 to 16 years) in Thailand who were at high risk of Hepatitis A Virus (HAV) infection. A total of 40,119 children were vaccinated with either HAVRIX or ENGERIX-B at 0, 1, and 12 months. 19,037 children received a primary course (doses at 0 and 1 months) of HAVRIX and 19,120 children received a primary course (doses at 0 and 1 months) of ENGERIX-B (FDA: Havrix).
Immune Response:
In response to vaccination, 32 cases of clinical hepatitis A occurred in the control group. In the HAVRIX group, 2 cases were identified. These 2 cases were mild in terms of both biochemical and clinical indices of hepatitis A disease.
Side Effects:
Side Effects of HAVRIX included: injection site pain, redness and swelling, irratibility, loss of appetite, and drowsiness.
Efficacy:
In response to vaccination, 32 cases of clinical hepatitis A occurred in the control group. In the HAVRIX group, 2 cases were identified. These 2 cases were mild in terms of both biochemical and clinical indices of hepatitis A disease. Therefore, the efficacy rate for prevention of clinical hepatitis A was 94% (FDA: Havrix).
t.
Human Response
Vaccination Protocol:
A multicenter study administered 720 EL.U./0.5mL of HAVRIX into infants 11 months and older. The same sample size and concentration was also administered in another study of infants 2 years of age and older (FDA: Havrix).
In the 11 months and older study, each infant was administered either HAVRIX or were coadministered HAVRIX and INFANRIX (Diphtheria and Tetanus Toxoids and Acellular Pertussis Vaccine Adsorbed) and Haemophilus influenzae type b (Hib) conjugate vaccine (tetanus toxoid conjugate).
Side Effects:
The most common side effects recorded with this dosage concentration and amount were: injection site pain, redness, swelling, irritability, drowsiness, and loss of appetite
u.
Human Response
Vaccination Protocol:
A clinical study of children 2 years and older administered HAVRIX at 360 EL.U, and were given the follow-up booster shots at 1 and 6 months after the initial shot (FDA: Havrix).
Immune Response:
After subjects were seropositive before each addtional booster was administered.
Side Effects:
Side effects recorded included: pain, and redness of the injection site, swelling, irritability, drowsiness and loss of appetite.
TWINRIX is a sterile suspension of inactivated hepatitis A virus (strain HM175) propagated in MRC-5 cells, and combined with purified surface antigen of the hepatitis B virus (FDA: TWINRIX).
l. Immunization Route
Intramuscular injection (i.m.)
m. Storage
TWINRIX should be refrigerated between 2° and 8° C (36° and 46° F). Do not freeze.
TWINRIX should not be administered to anyone with known hypersensitivity to any component of the vaccine, including yeast and neomycin and in patients with previous hypersensitivity to TWINRIX or monovalent hepatitis A or hepatitis B vaccines (FDA: Havrix).
p.
Human Response
Immune Response:
In clinical trials, it has been found that combining the hepatitis A antigen with the hepatitis B surface antigen in TWINRIX resulted in comparable anti-HAV or anti-HBsAg titers, relative to vaccination with the individual monovalent vaccines or the concomitant administration of each vaccine in opposite arms (FDA: TWINRIX).
Side Effects:
Side effects of immunization included: redness, itching and swelling of the injection site, headache and fatigue. Severe adverse effects were limited and resolved in a timely matter.
VAQTA [Hepatitis A Vaccine, Inactivated] is an inactivated whole virus vaccine derived from hepatitis A virus (HAV) grown in cell culture in human MRC-5 diploid fibroblasts. It contains inactivated virus of a strain which was originally derived by further serial passage of a proven attenuated strain. The virus is grown, harvested, purified by a combination of physical and high performance liquid chromatographic techniques developed at the Merck Research Laboratories, formalin inactivated, and then adsorbed onto amorphous aluminum hydroxyphosphate sulfate. One milliliter of the vaccine contains approximately 50 units (U) of hepatitis A virus antigen, which is purified and formulated without a preservative (FDA: VAQTA).
Hepatitis A vaccine should not be administered to persons with a history of a severe reaction to a prior dose of hepatitis A vaccine or to a vaccine component.
p. Description
Indication: Lowering the age indication for VAQTA from two years to 12 months of age (FDA: VAQTA).
VAQTA is indicated for active immunization against disease caused by hepatitis A virus in persons 12 months of age and older. Primary immunization should be given at least 2 weeks prior to expected exposure to Hepatitis A Virus (HAV).
q.
Human Response
Vaccination Protocol:
The protective efficacy, immunogenicity and safety of VAQTA were evaluated in a randomized, double-blind, placebo-controlled study involving 1037 healthy children and adolescents ages 2 through 16 years in a U.S. community with recurrent outbreaks of hepatitis A. Subjects were administered with either VAQTA or placebo (FDA: VAQTA)
Immune Response:
No cases of Hepatitis A have been confirmed in response to vaccination with VAQTA.
Side Effects:
Injection Site Reactions included: pain, redness and swelling. Systemic Reactions included: rash and fever.
Description:
The total duration of protective effect of VAQTA is unknown.
r.
Horse Response
Vaccination Protocol:
A clinical study was performed in 537 healthy adults, 18 to 83 years of age. The subjects were administered with a booster dose of VAQTA and HAVRIX†† (hepatitis A vaccine, inactivated) given at 6 or 12 months following an initial dose of HAVRIX (FDA: VAQTA).
Immune Response:
When VAQTA was given as a booster dose following HAVRIX, the vaccine produced an adequate immune response, seropositivity and booster response were both high in all subjects.
9. ViVaxim
a. Product Name:
Combined Purified Vi Polysaccharide Typhoid and Inactivated Hepatitis A Vaccine
