August 26, 2005
UNPROTECTED PEOPLE: Reports of
people who have suffered or died
from vaccine-preventable diseases
CDC REPORTS ON PREVENTABLE MEASLES AMONG
U.S. RESIDENTS, 2001-2004
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August 26, 2005
UNPROTECTED PEOPLE #79: CDC REPORTS ON PREVENTABLE MEASLES AMONG U.S.
The Immunization Action Coalition (IAC) publishes articles about people who
have suffered or died from vaccine-preventable diseases and periodically
devotes an IAC Express issue to such an article. This is the 79th in our
Indigenous measles has been eliminated in the United States, but cases
continue to be reported among U.S. residents. A CDC report indicates that
during 2001-2004, 177 measles cases were reported among U.S. residents. Of
these, 100 cases could have been prevented if current ACIP recommendations
had been followed, including specific guidelines for travelers.
During the study period, 46 cases of measles were reported among
unvaccinated infants. Of these, 17 had traveled internationally and were
among the population for whom ACIP recommends vaccination. Infants younger
than age one year who travel abroad are particularly vulnerable to measles
and should be vaccinated as early as age 6 months, as recommended. Adults
and children without confirmed immunity should be vaccinated with two doses
of measles vaccine, especially prior to international travel.
Titled "Preventable Measles Among U.S. Residents, 2001-2004," the report
appeared in MMWR on August 26, 2005. It is reprinted below in its entirety
with the exception of two tables, (1) "Preventable and nonpreventable
reported cases of measles in U.S. residents, by age, travel history, and
measles vaccination status--United States, 2001-2004" and (2) "Summary of
ACIP recommendations for measles-containing vaccine (MCV) for international
travelers, by age group," and footnotes and acknowledgments.
Elimination of endemic measles has been achieved in the United States;
however, measles continues to be imported from areas of the world where the
disease remains endemic, resulting in substantial morbidity and expenditure
of local, state, and federal public health resources. Measles among U.S.
residents results from returning residents who become infected while living
or traveling abroad, from contact or association with an infected traveler,
or from an unknown source. This report summarizes surveillance data reported
to CDC by state and local health departments regarding confirmed measles
cases among U.S. residents during 2001-2004; an illustrative case report is
included. The majority of measles cases occurring among U.S. residents can
be prevented by following current recommendations for vaccination, including
specific guidelines for travelers.
Confirmed measles cases were defined as preventable if they occurred among
persons for whom vaccination is recommended by the Advisory Committee on
Immunization Practices (ACIP) but who had not received 1 or more doses of
measles-containing vaccine (MCV). Cases were considered nonpreventable if
they occurred among persons who (1) had received 1 or more doses of MCV, (2)
were not vaccinated and for whom vaccination is not recommended, or (3) were
born before 1957 (presumed immune from natural disease in childhood).
Persons with unknown vaccination status were considered unvaccinated.
Outbreaks were defined as three or more epidemiologically linked cases.
During 2001-2004, a total of 251 measles cases were reported to CDC, of
which 177 (71%) occurred among U.S. residents, and 74 (29%) occurred among
nonresidents. Of the 177 cases among U.S. residents, 100 (56%) were
preventable, and 77 (44%) were nonpreventable.
Preventable cases. Of the 100 preventable cases, 43 (43%) occurred among
international travelers (imported cases), and 57 (57%) among nontravelers
(indigenous cases). Of the 17 (17%) preventable cases among infant travelers
aged 6-15 months, 12 occurred among infants aged 6-11 months, and five
occurred among children aged 12-15 months. Of the 83 (83%) preventable cases
among persons aged >=16 months, 26 were in persons who became infected
during international travel, and 57 were in persons infected in the United
Nonpreventable cases. Of the 77 cases that were nonpreventable, 12 (16%)
occurred among international travelers; 11 of the 12 travelers had received
at least 1 dose of MCV, and the other was born before 1957 and had not been
vaccinated. A total of 65 (84%) cases occurred among nontravelers; all were
in persons previously vaccinated, except 29 cases in infants aged <=15
months (routine MCV may be administered as late as age 15 months) and six in
persons born before 1957. Seven of the unvaccinated infants were aged 12-15
months and thus were eligible for vaccination.
Outbreaks. Of the 14 outbreaks identified during 2001-2004, nine involved
three or more U.S. residents; of these, seven originated with a U.S.
resident traveler. In one outbreak, 10 cases in a daycare center resulted
from exposure to an unvaccinated daycare attendee (an infant aged 9 months)
who was infected during travel abroad.
Case report. During June 20-22, 2004, a North Carolina resident aged 11
years traveled from the United Kingdom to North Carolina via New York and
Connecticut. After her arrival in North Carolina on June 22, she had cough,
coryza, and fever, followed by onset of a rash on June 25. She had suspected
measles diagnosed on June 28. She had not received MCV; her parents had
declined to have her vaccinated for religious beliefs. One day before her
rash onset, the girl had close contact with a male infant aged 11 months.
The infant subsequently had measles with rash onset on July 4. Two days
before his rash onset, the infant visited a summer camp, where he
potentially had contact with up to 234 persons, including 113 campers, 63
parents/visitors, and 58 staff members. Several campers returned home at the
end of the camp session, the day after the exposure. Multistate and
multinational investigation and control efforts to prevent further spread
were conducted. Potentially infected persons subsequently traveled to
Arizona, Arkansas, Florida, New York, Australia, Costa Rica, New Zealand,
South Africa, and Wales. No additional cases of measles were subsequently
Travel anywhere outside of the United States, including to industrialized
regions such as Western Europe, presents a risk for measles exposure. In
2003, approximately 24 million U.S. residents traveled abroad, and 40
million international visitors entered the United States. Importation of
measles from foreign visitors is unavoidable because no regulations are in
effect requiring vaccination of visitors. However, as other countries reduce
the burden of measles, the risk of travelers bringing measles into the
United States will decrease.
Measles can cause serious complications and death, particularly among
children aged <5 years. All U.S. residents should be vaccinated in
accordance with ACIP recommendations, with special attention to
international travelers who now account for a substantial proportion of the
measles disease burden in the United States. Healthcare providers who serve
populations that travel should be aware of the vaccination recommendations
for international travelers. Current measles recommendations for travelers
include vaccination for infants aged 6-11 months and 2 doses of MCV for
travelers aged >=12 months. Despite these recommendations, 17% of the
preventable cases described in this report occurred among unvaccinated
travelers aged 6-15 months. The reasons for these children not receiving MCV
are unknown but might include lack of awareness among parents and healthcare
providers regarding recommendations for infants aged 6-11 months, refusal
because of personal or religious beliefs, or lack of perceived risk,
especially for children of foreign-born U.S. residents who travel to their
country of origin. Imported and secondary cases among U.S. residents who
refuse vaccination because of personal or religious beliefs can result in
the introduction of measles into communities with other susceptible persons
who share the same beliefs, thereby posing a risk for substantial spread of
disease. In addition, seven cases in nontravelers aged 12-15 months might
have been prevented if these children had been vaccinated as soon as they
became eligible for MCV (e.g., MMR) at age 12 months.
Measles cases among persons born before 1957 for whom vaccination is not
recommended are rare. However, persons in this age group who travel
internationally might wish to consider vaccination to minimize their risk
The findings in this report are subject to at least three limitations.
First, certain measles cases might have been missed or not reported to
public health officials, including cases that occurred and resolved during
travel abroad. Second, because information on multiple doses of MCV is
collected inconsistently, persons who had received at least 1 dose of MCV
were considered vaccinated, even though 2 doses are recommended for some age
groups and for most international travelers, thus potentially
underestimating the number of preventable cases. Third, preventable cases
might be overestimated because vaccine efficacy is <100%, and vaccination
data were missing for 30 (17%) persons. All persons with missing data were
considered unvaccinated, although some might have received MCV.
Because of the high infectivity and morbidity associated with measles,
contact tracing is a standard public health practice and can require many
hours of public health staff time and can cost thousands of dollars. A
recent study evaluating the economic impact of an infected U.S. traveler
returning from India estimated the costs of locating and vaccinating
susceptible contacts at $140,000. Although few cases have been associated
with transmission during air travel (CDC, unpublished data, 2005), contact
tracing of infected air travelers is particularly challenging; a person with
measles can be infectious from at least 4 days before through 4 days after
rash onset. To avoid outbreaks or a resurgence of measles, as occurred
during 1989-1991, when approximately 55,000 cases and 120 measles-related
deaths were reported in the United States, high population immunity and
surveillance must be maintained.
To prevent measles among U.S. residents, healthcare providers should follow
ACIP vaccination recommendations, ensuring that travelers are vaccinated,
particularly infants aged 6-11 months, and that 2 doses are administered for
those aged >=12 months. In addition, parents should be educated about the
risk for measles associated with international travel and the need for
vaccination. Information on vaccination recommendations for travelers is
available from CDC at
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