Hepatitis A Vaccination: Who Needs It and When?

Hepatitis A is an acute viral liver infection transmitted by the fecal-oral route through close contact and contaminated food or water. The disease is self-limiting in most people, but the risk of severe disease increases with age and chronic liver disease. Specific prevention involves inactivated hepatitis A vaccines, which provide lasting immunity after a two-dose course. [1]

The international epidemiology is changing: improved sanitation is reducing the overall circulation of the A virus, but the proportion of people without immunity is increasing in older age groups. This is shifting the incidence of the disease to older ages, where the risk of complications is higher, and increasing the value of routine vaccination and pre-travel immunization. [2]

Hepatitis A vaccines are inactivated: they do not contain live virus and do not cause disease. Immunogenicity is high after the first dose, and a two-dose course provides long-term protection; revaccination is not routinely required. [3]

Who is eligible for vaccination?

Routine vaccination is recommended for all children aged 12–23 months, with the option of catch-up immunization up to age 18. Adults are vaccinated according to risk indications and for anyone wishing protection. Key groups include travelers to regions of moderate and high endemicity, people with chronic liver disease, people with HIV infection, men who have sex with men, people who use drugs, people without a permanent home, contacts of international adoptions, and any unvaccinated person who desires individual protection. [4]

During outbreaks, immunization covers all risk groups over 1 year of age. In institutions where the proportion of patients with risk factors is high, proactive vaccination programs are recommended. [5]

Serological screening prior to vaccination is not mandatory, but may be useful in older adults or when resources are limited to avoid unnecessary doses in those with pre-existing immunity.[6]

Vaccines and their composition: what is available and how they differ

All registered monovalent hepatitis A vaccines are inactivated preparations adsorbed on aluminum hydroxide. The most common trade names are Havrix, Vaqta, and Avaxim in some countries. They differ in strains, antigen dose, and excipients, but are interchangeable in dosage. [7]

Some syringe caps and stoppers in some batches may contain dry natural rubber. Some vaccines may contain traces of neomycin. If you are allergic to any of the components, caution is advised or an alternative should be chosen. [8]

Table 1. Core hepatitis A vaccines and dosages

Vaccine	Age	Dose and volume	Well	Interval between doses
Havrix	1-18 years old	720 units in 0.5 ml	2 doses	6-12 months
Havrix	≥19 years old	1440 units in 1.0 ml	2 doses	6-12 months
Vaqta	1-18 years old	25 units in 0.5 ml	2 doses	6-18 months
Vaqta	≥19 years old	50 units in 1.0 ml	2 doses	6-18 months
Twinrix (combination A + B)	≥18 years old	1.0 ml	3 or 4 doses	standard 0-1-6 months, accelerated 0-7-21-30 days + 12 months

Efficiency and duration of protection

Just one month after the first dose, more than 90% of vaccinated individuals have protective antibody levels, and by the time of the second dose, the immune response is strengthened. A two-dose course provides long-term protection for at least decades; in observations after 20 years, more than 97% of adults remained seropositive, and modeling predicts that protective levels will be maintained in most individuals for 30-40 years. Scheduled boosters are not required after the course is completed. [9]

Even a single dose demonstrates high short- and medium-term protection and is used for rapid prophylaxis in outbreaks and for post-exposure immunization, but for long-term immunity the course must be completed. [10]

Vaccination schedules: standard and catch-up

The basic course of monovalent vaccines consists of two doses, separated by a minimum interval of six months. If the series is interrupted, it is not restarted: the second dose is administered at the earliest opportunity, maintaining the minimum interval. Interchangeability between brands within the same course is possible. [11]

For the combined hepatitis A and hepatitis B vaccine, a standard 0-1-6 month schedule and an accelerated "last minute" schedule with injections on day 0, day 7, and days 21-30, with a mandatory booster at 12 months, are available. There are no accelerated schedules for the monovalent hepatitis A vaccines. [12]

Table 2. Practical vaccination schedules

Scenario	Preparation	How many doses?	When to enter
Routinely for children 12-23 months	Havrix or Vaqta	2	0 months and after 6-18 months
Catching up to 18 years old	Havrix or Vaqta	2	0 months and at least 6 months
Adult before travel in 3-4 weeks	Twinrix	4	Day 0, Day 7, Days 21-30, Booster after 12 months
Interrupted course	Any monovalent vaccine	1	Give the missing second dose at the earliest opportunity, do not start over

Post-exposure prophylaxis and emergency protection

In case of contact with a confirmed case, unvaccinated individuals aged 12 months and older are recommended to receive a single dose of the monovalent vaccine as soon as possible, optimally within 14 days. For individuals with immunosuppression, chronic liver disease, and some individuals over 40 years of age, human immunoglobulin may be administered simultaneously with the vaccine at a dose of 0.1 milliliters per kilogram into different anatomical sites. Infants under 12 months of age and those for whom the vaccine is contraindicated are administered immunoglobulin alone. The combination vaccine is not used for post-exposure prophylaxis. [13]

For pre-exposure protection when vaccination is not possible, the use of immunoglobulin is permitted: 0.1 milliliters per kilogram for trips up to 1 month, 0.2 milliliters per kilogram up to 2 months, for longer trips - 0.2 milliliters per kilogram every 2 months. [14]

Table 3. Post-exposure prophylaxis (quick reminder)

Group	What to enter	Dose of immunoglobulin	When
≥12 months, no contraindications	Vaccine	Not required	As soon as possible, within 14 days
≥12 months, immunodeficiency or chronic liver disease	Vaccine + immunoglobulin	0.1 ml per kg	At the same time, in different places
>40 years, according to risk assessment	Vaccine ± immunoglobulin	0.1 ml per kg	Individually, preferably up to 14 days
<12 months or contraindications to the vaccine	Immunoglobulin	0.1 ml per kg	As soon as possible, within 14 days

Safety, tolerability and contraindications

The vaccines are well tolerated. The most common reactions are pain, redness, and swelling at the injection site, short-term headache, malaise, and low-grade fever. Serious adverse events are extremely rare. Clinical protocols should include readiness for immediate treatment in the event of anaphylaxis. [15]

Contraindications: Severe allergic reaction to a previous dose or to any component of the vaccine. Acute severe illnesses with fever should be postponed until recovery. If you have a latex allergy, check the specific batch packaging. If you have a severe allergy to neomycin, avoid vaccines containing traces of it. [16]

Table 4. Frequent post-vaccination reactions

Reaction	How often	What to do
Soreness at the injection site	Often	Usually does not require treatment, if necessary local cold, oral pain reliever
Redness and hardening	Often	Observation, symptomatic
Headache, fatigue	Often	Symptomatic, usually 1-2 days
A slight increase in temperature	Often	Observation, antipyretic drug if necessary
Urticaria, anaphylaxis	Very rarely	Immediate medical care according to standards

Special groups and clinical situations

Pregnancy and lactation. Inactivated vaccines are theoretically safe during pregnancy and are used for risky indications, including travel and high risk of severe liver disease. Breastfeeding is not a contraindication. [17]

Immunodeficiency. The immune response may be reduced, but inactivated vaccines are permitted. In cases of exposure or high risk, immunoglobulin is added. Separate guidelines for people with HIV and after transplantation recommend a course with serological monitoring and, if necessary, additional doses. [18]

Chronic liver disease. Vaccination is a priority, as hepatitis A often has a severe course in this group. The immune response is generally adequate, and safety is comparable to that of the general population. [19]

Children aged 6-11 months before travel. A single dose of the monovalent vaccine is allowed for protection during travel, but it is not counted toward the routine course. From 12 months, the full two doses begin. [20]

Table 5. Solutions for special groups

Situation	Tactics	Notes
Pregnancy with high risk of exposure	Vaccine according to indications	Inactivated drug
HIV infection	Full course, risk control	A decreased response is possible; add immunoglobulin upon contact.
Chronic liver disease	Full course priority	Add immunoglobulin upon contact.
Early infant 6-11 months, travel	One dose before travel	Not included in the routine course, start with 2 doses from 12 months

Compatibility, interchangeability and documentation

The Havrix and Vaqta monovalent vaccines are interchangeable within the course. The combination vaccine is not used for post-exposure prophylaxis, but is convenient for adults who require simultaneous protection against hepatitis A and hepatitis B. Simultaneous administration with other inactivated and live vaccines is possible at different anatomical sites. [21]

After the administration of immunoglobulin, interactions with live measles, rubella, and chickenpox vaccines should be considered: these should be delayed for at least 6 months. If immunoglobulin is administered within 2 weeks of these vaccines, a booster dose should be scheduled later. [22]

Table 6. Interchangeability and combinations

Question	Answer
Is it possible to complete the course with a different brand of monovalent vaccine?	Yes
Can a combination vaccine be used for post-exposure prophylaxis?	No
Can it be administered simultaneously with other vaccines?	Yes, in different areas
What to consider when administering immunoglobulin	Postpone live vaccines for at least 6 months

Practical steps: how to organize vaccination

Step 1. Assess the indication: age, risk factors, travel plans. If necessary, consider serologic screening for total anti-HAV to avoid unnecessary doses in already immune adults. [23]

Step 2. Select the vaccine and schedule. For urgent travel, adults may benefit from the combination vaccine, administered with an accelerated schedule and a booster dose 12 months later. For standard cases, a single-dose vaccine administered in two doses at least 6 months apart is recommended. [24]

Step 3. Administer the vaccine into the deltoid muscle, recording the brand name, batch number, date, volume, injection site, and patient information. In cases of risk of exposure or in immunocompromised groups, consider supplementing with immunoglobulin at the dosages listed in the table. [25]

Table 7. Documentation of vaccination

Field	What to write down
Date and time	Day, month, year
Preparation	Trade name, manufacturer
Batch and expiration date	Full codes
Dose and volume	In milliliters
Place of administration	Left or right deltoid muscle
Reactions	Presence and nature

Frequently asked questions

How quickly does protection develop after the first dose? Most people achieve protective antibody levels within 2-4 weeks; some adults experience seroconversion by day 15. For long-term protection, the course must be completed. [26]

Are booster doses necessary after years? Boosters are not recommended after completing a course. Immunological memory is preserved, and protection is long-lasting. [27]

Is it possible to get vaccinated "at the last minute" before departure? Yes, even on the day of departure, the first dose is beneficial. If you need rapid protection against both hepatitis A and hepatitis B, adults can receive an accelerated combination vaccine with a subsequent booster dose 12 months later. [28]

What to do if you have had close contact with a sick person. The sooner the better: administer a monovalent vaccine within 14 days, and for those with immunosuppression or chronic liver disease, add immunoglobulin. Infants under 12 months are given only immunoglobulin. [29]

Table 8. When to seek immediate medical attention

Situation	Why is this important?
Symptoms of hepatitis after exposure	Diagnosis and post-exposure prophylaxis are required.
Severe allergic reaction after vaccination	Emergency assistance needed
Upcoming travel to a region of moderate or high endemicity	Timely vaccination is necessary
Chronic liver disease without immunization	High risk of severe disease, vaccination is a priority

Table 9. Minimum intervals and key dosages

Parameter	Meaning
Minimum interval between 1 and 2 doses of monovalent vaccines	6 months
Dose of immunoglobulin for post-exposure prophylaxis	0.1 ml per kg
Dose of immunoglobulin for travel up to 1 month	0.1 ml per kg
For trips up to 2 months	0.2 ml per kg
Trips longer than 2 months	0.2 ml per kg every 2 months