Version May 2024
INTRODUCTION — Each year thousands of children immigrate to the United States through international adoption. Internationally adopted children are at increased risk for common infectious diseases such as tuberculosis, intestinal parasites, skin infections, and infestations because they come from resource-poor countries where these conditions are common. Assuring that these children are protected against vaccine-preventable diseases often can be challenging. Many internationally adopted children have poor documentation of immunizations from their birth country or may not have had the opportunity to have received the vaccines routinely given in the United States.
Immunization of internationally adopted children and their close contacts will be discussed here. Infectious diseases in international adoptees and general issues related to adoption are discussed separately. (See "International adoption: Infectious disease aspects" and "Adoption".)
IMMUNIZATIONS FOR INTERNATIONAL ADOPTEES
Immunizations in the country of origin — Routine immunization schedules vary from country to country and are available for specific countries through the World Health Organization (WHO). Most children arrive to the United States with documentation of some immunizations from their birth country. Children often receive some immunizations during the exit evaluation in their country of origin.
Internationally adopted children typically have had the opportunity to receive the following immunizations in their countries of origin (table 1) [1]:
●Bacillus Calmette-Guérin
●Diphtheria, tetanus, and pertussis
●Poliovirus
●Hepatitis B
●Measles (with or without mumps and rubella)
Some countries may also immunize against Haemophilus influenzae type b (Hib). Increasingly, other vaccines such as pneumococcal conjugate, rotavirus, hepatitis A virus, influenza, and varicella vaccines are being administered to young children in the countries from which international adoption to the United States occur.
Countries of origin may use vaccines that differ from those administered in the United States (eg, bivalent oral poliovirus vaccine [OPV] rather than trivalent inactivated poliovirus vaccine [IPV]; whole-cell rather than acellular pertussis-containing vaccines; monovalent measles vaccine rather than combination measles, mumps, rubella vaccine, etc). They also may have different contraindications (eg, encephalopathy and congenital heart disease, which are contraindications to vaccination in China), which may contribute to lack of immunization [2].
The Immigration and Nationality Act of 2009 stipulates that anyone seeking residence in the United States must show proof of age-appropriate vaccination as recommended by the Centers for Disease Control and Prevention (CDC) Advisory Committee on Immunization Practices [3,4]. However, parents of internationally adopted children younger than 10 years may obtain a waiver allowing them to receive the first dose of these vaccines within 30 days of their arrival to the United States.
Immunization after adoption — Internationally adopted children should be immunized according to the United States' recommended schedule for healthy infants, children, and adolescents (figure 1A-B).
It can be challenging for clinicians to determine which immunizations are necessary. Most international adoptees have some documentation of receipt of immunizations, but the documentation may not be complete or reliable [5,6]. In addition, vaccine response may be suboptimal because of poor vaccine storage, inadequate vaccine intervals, or malnutrition [7].
The approach to immunizing internationally adopted children depends upon the availability and quality of documentation of immunizations administered in the home country. Only written documentation should be accepted as evidence of previous immunization [6,8-10].
Documentation of a clinical diagnosis of measles, mumps, rubella, varicella, or hepatitis A from the child's country of origin should not be accepted as evidence of immunity [11].
Valid immunization record — Written records may be considered valid if the vaccines, dates of administration, numbers of doses, intervals between doses, and age of the patient at the time of immunization are comparable to United States (figure 1A-B) or WHO schedules [10].
●For poliovirus immunization, this requires immunization with trivalent IPV or trivalent oral poliovirus vaccine (tOPV); doses of OPV administered on or after April 1, 2016 should not be counted (they are presumed to be bivalent OPV or monovalent OPV) [12].
●For hepatitis A immunization, this requires immunization with a vaccine other than Aimmugen or Twinrix Jr [10]. Twinrix Jr is a combination hepatitis A/hepatitis B vaccine; the hepatitis B component can be counted as valid, but not the hepatitis A component because it contains less hepatitis A antigen than hepatitis A vaccinees used for children in the United States.
A chart with the terms used for vaccine-preventable diseases in various languages is available through Immunize.org.
Children who have an adequate written immunization record for vaccines received in the home country but whose immunizations are not up-to-date should receive catch-up immunizations as appropriate for their age (table 2A-B).
Several studies evaluating serologic testing to verify the immunization status or immune response to vaccine-preventable diseases in internationally adopted children have inconsistent findings [5,13-25]. Differences in study design and laboratory methods may account for the different results from these studies. In the largest study, international adoptees with documentation of ≥3 doses of diphtheria, tetanus, pertussis, poliovirus, hepatitis B, and Hib and, for children ≥12 months, ≥1 dose of measles, mumps, rubella, and varicella in their home country were more likely to have protective antibody than those without documentation, as illustrated below [23]:
●Diphtheria – 85 versus 69 percent
●Tetanus – 95 versus 76 percent
●Poliovirus – 93 versus 83 percent
●Hepatitis B – 77 versus 42 percent
●Hib – 67 versus 27 percent
●Measles – 95 versus 58 percent
●Mumps – 72 versus 31 percent
●Rubella – 94 versus 30 percent
●Varicella – 38 versus 33 percent; 83 percent of children with a history of varicella disease were immune to varicella
The number of recorded doses was the best predictor of protective antibody [23,24]. Protective antibody levels among adoptees without documentation of adequate immunization indicate either history of disease or undocumented receipt of vaccines.
Unknown or uncertain immunization — For children who do not have a valid immunization record, or whose immunization status is unknown, uncertain, or does not adhere to the United States (figure 1A-B) or WHO schedules, revaccinating (as if the child were unvaccinated), serologic testing for antibodies to vaccine-preventable illnesses (table 3), or a combination of the two approaches is reasonable [6,8]. The CDC Advisory Committee on Immunization Practices generally recommends age-appropriate revaccination (table 4) [10,26].
Factors to be considered in the decision include [27]:
●The age of the child (the older the child they more likely they will have immunity)
●The number of doses and visits necessary for completion (taking into consideration the time and cost of visits that may not be necessary if the child is immune)
●Whether the child's adjustment will be adversely affected by multiple injections and doctor visits
●The availability and cost of serologic testing
●Urgency for school entry (it may take a long time to complete all necessary immunizations)
Serologic testing — Serologic testing can be performed to evaluate whether children have protective levels of antibody from immunization or past infection for some vaccine-preventable illnesses (table 3). Protective levels of antibody may avoid unnecessary reimmunization. However, serologic testing is not always readily available and may be expensive [27].
Antibody levels do not differentiate past disease from immunization, except for hepatitis B (table 5). To assure long-term protection, children who have protective antibody levels and are younger than the recommended age for booster doses (eg, four to six years for diphtheria, tetanus, and pertussis) should receive the subsequent booster dose(s) at the recommended age (figure 1A-B), as well as other vaccines that are initiated at a later age such as tetanus-diphtheria-acellular pertussis, the human papillomavirus series, and meningococcal vaccine.
Additional caveats regarding serology for specific antigens are provided below:
●Diphtheria, tetanus, and hepatitis B virus – Testing for antibody to diphtheria, tetanus, and hepatitis B can be performed in children ≥5 months of age.
●Pertussis – Serologic testing is not widely available for pertussis. However, documented immunity to diphtheria and tetanus (ie, >0.1 international unit/mL) can be used as a surrogate marker for immunity to pertussis because diphtheria, tetanus, and pertussis usually are administered in combination (eg, as diphtheria, tetanus, acellular pertussis vaccine or diphtheria, tetanus, whole cell pertussis vaccine) [7]. However, the child's age and antibody level must be taken into consideration. As an example, acellular pertussis-containing immunization may be warranted in a two-year old who has protective but low antibody concentrations to diphtheria and tetanus (eg, <0.4 international units/mL) because their immunity to pertussis is likely to wane before the four-year booster dose.
●Poliovirus – Serologic testing for poliovirus is no longer recommended. Testing for antibodies to poliovirus type 2 is not available, and demonstration of antibodies to polioviruses 1 and 3 does not reliably indicate protection against poliovirus type 2 [12].
●H. influenzae type b – Serologic testing for antibodies to Hib can also be performed in children ≥5 months. However, given that most children arrive to the United States after 12 months of age, it may be preferable to provide age-appropriate immunization for Hib rather than obtaining Hib serology.
●Measles, mumps, rubella, varicella, hepatitis A – Testing for antibody to measles, mumps, rubella, varicella, and hepatitis A should not be performed before 12 months of age because of the possibility of persistent maternal antibody.
Two doses of measles-mumps-rubella (MMR) vaccine are necessary if the child lacks protective levels of antibody to measles or mumps (even if they have protective levels of antibody to the other antigen and to rubella). Only one dose of MMR is necessary if the child has protective levels of antibody to measles and mumps but lacks protective levels of antibody to rubella. (See "Measles, mumps, and rubella immunization in infants, children, and adolescents", section on 'Catch-up immunization'.)
●Other antigens – Age-appropriate immunization with pneumococcal conjugate, rotavirus, poliovirus, and influenza vaccines is recommended. These vaccines are not routinely administered in the countries of origin, and serologic testing is not practical since the pneumococcal vaccine has at least 10 serotypes, there is no correlate of protection for rotavirus vaccine (and it should not be given if the child is >8 months of age), and influenza vaccine is an annual vaccine. (See "Seasonal influenza in children: Prevention with vaccines", section on 'Schedule' and "Rotavirus vaccines for infants", section on 'Schedule' and "Pneumococcal vaccination in children", section on 'Routine immunization for children <5 years'.)
Revaccinating — Immunizations that are not documented or do not adhere to the United States (figure 1A-B) or WHO schedules should be repeated if serologic testing is not or cannot be done. Age-appropriate immunization (or reimmunization) of internationally adopted children with unknown or uncertain immunization status as if they have received no immunizations (table 2A-B) is an alternative to serologic testing for diphtheria, tetanus, hepatitis A and B, measles, mumps, rubella, varicella, and Hib. Reimmunization is recommended for poliovirus and Streptococcus pneumoniae. Most children come to the United States outside the age range for rotavirus vaccine (>8 months of age) and influenza vaccine is an annual vaccine.
Repeating immunizations that have already been administered is generally considered safe. However, children younger than seven years should not receive more than six doses of diphtheria- and tetanus toxoid-containing vaccines (eg, diphtheria and tetanus toxoids [without pertussis]; diphtheria toxoid, tetanus toxoid, and acellular pertussis vaccine; diphtheria toxoid, tetanus toxoid, and whole cell pertussis vaccine) because of the risk of local and systemic reaction [28,29]. For children being revaccinated against diphtheria, tetanus, and pertussis who develop a severe local reaction, the CDC Advisory Committee on Immunization Practices recommends serologic testing for immunoglobulin G antibody to tetanus and diphtheria toxins before administering additional doses [10].
IMMUNIZATIONS FOR FAMILY MEMBERS AND CONTACTS
Routine immunizations — Adult and pediatric family members and close contacts of international adoptees should be current for routine immunizations (figure 1A-C) before the adoptee joins the household [9,10]. The need for immunization is highlighted by reports of vaccine-preventable diseases brought into the United States and transmitted by internationally adopted children [2,30-40].
Adult contacts of international adoptees frequently need the following vaccines before the child's arrival:
●Tetanus toxoid-reduced diphtheria toxoid-acellular pertussis, which serves as a tetanus booster and provides protection against pertussis (see "Tetanus-diphtheria toxoid vaccination in adults")
●A second measles-mumps-rubella (MMR) vaccine (if born after 1957) (see "Measles, mumps, and rubella immunization in adults", section on 'Who should be immunized')
●Varicella vaccine (if they have no history of varicella disease or immunization) (see "Vaccination for the prevention of chickenpox (primary varicella infection)", section on 'Evidence of immunity')
●Influenza vaccine (see "Seasonal influenza vaccination in adults")
For pediatric contacts of international adoptees whose immunizations are not current, the routine schedule may be accelerated to improve protection (table 2A-B). Certain vaccines can and should be given earlier than recommended in the routine schedule. For example, if a child <12 months of age is traveling, one dose of MMR should be given; two additional doses will still be needed after 12 months of age. For children >12 to 48 months of age, the second measles vaccine should be given early (one month after the initial vaccine) and will not need to be repeated at four to six years of age. Similarly, the second varicella vaccine should be given prior to travel as well (>3 months after the initial dose).
Hepatitis A vaccine — Hepatitis A vaccine is recommended for previously unvaccinated family members and close contacts of internationally adopted children [41,42]. In the United States, hepatitis A vaccine has been routinely recommended for children ≥12 months of age since 2006 [42]. Children and adults born before 2006 may not have received hepatitis A vaccine.
The first dose of hepatitis A vaccine provides protection before the arrival of the child; a second dose, given at least six months after the first, provides long-term protection. (See "Hepatitis A virus infection: Treatment and prevention", section on 'Protection prior to exposure'.)
Hepatitis A is prevalent in resource-poor countries and can be transmitted through ingestion of contaminated food and water or feces. Outbreaks of hepatitis A associated with internationally adopted children led to the recommendations for immunization for traveling and nontraveling family members and close contacts of international adoptees children [42]. (See "Overview of hepatitis A virus infection in children", section on 'Epidemiology'.)
Hepatitis B vaccine — Hepatitis B vaccine is not routinely recommended for adults in the United States unless they are in a risk category (eg, health care practitioner, intravenous drug user, household contact with acute or chronic hepatitis B virus infection, etc). We suggest that family members (adults and children) of internationally adopted children be vaccinated against hepatitis B virus before the child's arrival. To allow adequate time for response, the first dose of hepatitis B vaccine should be administered at least six months before the child joins the family [43]. (See "Hepatitis B virus immunization in adults" and "Hepatitis B virus immunization in infants, children, and adolescents", section on 'Catch-up immunization'.)
Unvaccinated contacts of internationally adopted children who have acute or chronic hepatitis B virus infection (ie, those who are hepatitis B surface antigen-positive) must be vaccinated promptly. Hepatitis B virus is easily transmitted to household contacts, and transmission of hepatitis B from newly adopted children to their parents has been documented [33,35]. (See "Epidemiology, transmission, and prevention of hepatitis B virus infection".)
Additional immunizations for travel — Adult and pediatric family members and close contacts of international adoptees who are traveling to meet and/or accompany the international adoptee to the adoptive country should receive vaccines for travel as recommended by the Centers for Disease Control and Prevention. Health care providers should review the recommendations for travel immunizations several months before travel so that immunizations can be provided or updated as necessary before travel [9]. The Pre-travel Providers' Rapid Evaluation Portal is a clinical tool that helps health care providers prepare travelers from the United States for international travel. (See "Immunizations for travel".)
In addition to routine immunizations (particularly measles) and hepatitis A and B vaccines, immunizations recommended before travel may include [44]:
●Inactivated poliovirus vaccine may be recommended for adult travelers to some countries (see "Immunizations for travel" and "Immunizations for travel", section on 'Poliovirus vaccine')
●Typhoid vaccine for some countries; a parenteral polysaccharide vaccine can be given for travelers ≥2 years of age and a live-attenuated oral vaccine can be given to travelers ≥6 years of age (see "Immunizations for travel", section on 'Typhoid vaccine')
●Yellow fever vaccine is recommended for some regions in Africa and South America (see "Immunizations for travel", section on 'Yellow fever vaccine')
●Meningococcal vaccine for certain countries in Africa and India (see "Immunizations for travel", section on 'Meningococcal vaccine')
●Japanese encephalitis vaccine for certain travelers to Asia depending upon destination, duration, season, and activities (see "Immunizations for travel", section on 'Japanese encephalitis vaccine')
SARS-CoV-2 IMMUNIZATION AND TESTING — Families traveling to adopt may need to provide proof of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) immunization (if eligible for immunization) and a negative SARS-CoV-2 test before travel to the country of origin and/or upon return to the United States. The Centers for Disease Control and Prevention provides additional travel recommendations for specific destinations, as does the International Travel Advisory.
SARS-CoV-2 immunization is discussed separately. (See "COVID-19: Vaccines".)
RESOURCES — A number of resources that may be helpful for health care providers or parents of international adoptees are available (table 6).
SUMMARY AND RECOMMENDATIONS
●Immunizations in the country of origin – The routine immunization schedule varies from country to country. Routine immunization schedules for specific countries are available through the World Health Organization (WHO). Internationally adopted children typically have had the opportunity to receive Bacillus Calmette-Guérin, diphtheria, tetanus, pertussis, poliovirus, hepatitis B virus, and measles (with or without mumps and rubella) vaccines before adoption. (See 'Immunizations in the country of origin' above.)
●Immunization after adoption
•Internationally adopted children should be immunized according to the United States' recommended schedule for healthy infants, children, and adolescents (figure 1A-B). Immunization must be initiated within 30 days of arrival (if not before). (See 'Immunization after adoption' above.)
•The approach to immunizing internationally adopted children depends upon the availability and quality of documentation of immunizations from the home country. (See 'Immunization after adoption' above.)
•Written records may be considered valid if the vaccines, dates of administration, numbers of doses, intervals between doses, and age of the patient at the time of immunization are comparable to the United States (figure 1A-B) or WHO schedules.
-For poliovirus immunization, this requires immunization with trivalent inactivated poliovirus vaccine or trivalent oral poliovirus vaccine.
-For hepatitis A immunization, this requires immunization with a vaccine other than Aimmugen or Twinrix Jr [10]. Twinrix Jr is a combination hepatitis A/hepatitis B vaccine; the hepatitis B component can be counted as valid, but not the hepatitis A component.
Children who have an adequate written documentation of immunization but whose immunizations are not up-to-date should receive age-appropriate catch-up immunizations (table 2A-B). (See 'Valid immunization record' above.)
•For children whose immunization status is unknown or uncertain, serologic testing for antibodies to vaccine-preventable illnesses (table 3), revaccinating (as if the child were unvaccinated), or a combination of the two approaches may be undertaken. (See 'Unknown or uncertain immunization' above.)
●Immunizations for family members and contacts – Adult and pediatric family members and close contacts of international adoptees should be up-to-date with routine immunizations before the adoptee joins the household (figure 1A-C). Previously unvaccinated family members and close contacts also should receive hepatitis A and hepatitis B vaccines before the arrival of the adoptee. (See 'Routine immunizations' above and 'Hepatitis A vaccine' above and 'Hepatitis B vaccine' above.)
Adult and pediatric family members and close contacts of international adoptees who are traveling to meet and/or accompany the international adoptee to the adoptive country should receive vaccines for travel as recommended by the Centers for Disease Control and Prevention. (See 'Additional immunizations for travel' above.)
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