Review
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Feasibility of global measles
eradication after interruption
of transmission in the Americas
Expert Rev. Vaccines 7(3), 355–362 (2008)
Ciro A de Quadros†,
Jon Kim Andrus,
M Carolina
Danovaro-Holliday
and Carlos
Castillo-Solórzano
†
Author for correspondence
Sabin Vaccine Institute,
Washington, DC 20006, USA
Tel.: +01 202 265 6515
[email protected]
Measles is one of the most infectious diseases. Before the introduction of the measles vaccine,
nearly all children contracted measles. By the end of the 1980s, most countries of the world
had incorporated the measles vaccine into their routine vaccination programs. Globally, some
345,000 deaths due to measles still occur every year. Eradication of measles would play an
important role in improving child survival. The goal to eradicate measles from the Americas
was set by the Pan-American Sanitary Conference in 1994. Progress to date has been
remarkable. Measles is no longer an endemic disease in the Americas and interruption of
transmission has been documented in most countries. As of December 2007, 5 years have
elapsed since the detection of the last endemic case in Venezuela in November 2002. This
experience demonstrates that interruption of measles transmission can be achieved and
sustained over a long period of time. Global eradication should be feasible if the appropriate
strategies are implemented. Even in a new paradigm in which eradication is not followed by
the discontinuation of vaccination, eradication of measles should be a good investment to
avoid expensive epidemics and save those children that would potentially die due to infection
with the measles virus. It is not only a dream to think that we will see a world free of measles
by the year 2015.
KEYWORDS: Americas • eradication • measles • transmission • vaccination
Measles is one of the most infectious diseases.
Before the introduction of the measles vaccine,
nearly all children contracted measles. Human
beings are the only reservoir of measles,
although other primates, such as monkeys, can
also have the infection. The most infectious
phase is the prodromic one, approximately
4 days before fever and exanthema appear. The
communicability diminishes rapidly after the
appearance of exanthema [1].
By the end of the 1970s, an attenuated live
measles virus vaccine, which was authorized for
use in the USA in 1963, had been widely
administered in some parts of the world. It is
believed that the immunity conferred by the
vaccine lasts for the entire life [2]. Its effectiveness is approximately 90–95%. Due to the
interference of maternal antibodies, the effectiveness of the vaccine increases after the first
6 months of life, peaking at approximately
95% at 12–15 months of age [3]. By the end of
the 1980s, most countries of the world had
incorporated measles vaccines into their routine
www.future-drugs.com
10.1586/14760584.7.3.355
vaccination programs, and coverage with this
vaccine has increased considerably. By 1990,
the world reported measles vaccination coverage of children aged 2 years to be approximately 70%; by 2005 this coverage increased to
an estimated 77% [101].
Data from the WHO indicate that in 1999
measles was responsible for 10% of deaths
worldwide among children aged less than
5 years. At the beginning of this decade, some
40 million cases and 800,000 deaths due to
measles still occurred each year; and more
than half of the deaths occurred in Africa. As
a result of efforts by the global coalition of
partners – Ministries of Health, the WHO,
UNICEF, the US CDC and the American
Red Cross – measles mortality in Africa was
reduced from 506,000 in 1999 to 126,000 in
2005. The strategies used were similar to
those used in the Americas. Achieving zero
cases of measles and, ultimately, the eradication of measles virus transmission, would play
an important role in improving child survival
© 2008 Future Drugs Ltd
ISSN 1476-0584
355
Review
de Quadros, Andrus, Danovaro-Holliday & Castillo-Solórzano
Reported cases (thousands)
6
Measles eradication in the
Western hemisphere
100
5
80
Keep up
4
60
3
MMR vaccine coverage (%)
globally. The purpose of this paper is to
review the experience of measles eradication in the Americas to better understand whether global eradication of
measles is feasible.
356
8
19 5
87
19
89
19
91
19
93
19
9
19 5
97
19
99
20
01
20
03
20
05
20
07
83
19
81
19
79
19
77
19
75
19
73
19
19
20
0
20 4
07
00
96
20
92
19
88
19
84
19
80
19
76
19
72
19
68
19
64
19
19
19
60
Coverage (%)
Rate (per 100,000
population)
19
71
Catch-up
40
The goal to eradicate measles from the
Follow-up vaccination
vaccination
2
Western hemisphere was set by the PanAmerican Sanitary Conference in 1994,
20
1
at the same time that that the International Commission for Certification of
0
0
Poliomyelitis declared the region free
from polio [4]. The rationale for the strategy used to achieve this goal was based on
Year
the epidemiology of measles before and
after the vaccine was introduced. Before
2. Reported measles cases by month, Cuba, 1971–2007*.
the vaccine was introduced, measles epi- Figure
*
Coverage data not available.
demics occurred every few years (FIGURE 1). MMR: Measles–mumps–rubella.
Epidemics occurred when the pool of Source: Ministry of Health, Cuba.
susceptibles provided by each birth
cohort was of sufficient size to fuel transmission when the
A considerable number of children remain susceptible
virus was introduced in a given population. After the intro- because they never received the vaccine. Since vaccine effectiveduction of the vaccine, and with subsequent increases in vac- ness is not 100%, a small proportion of those vaccinated who
cination coverage, the interepidemic periods lengthened, were primary failures also remain susceptible, adding to the
sometimes stretching for several years between one epidemic accumulating total pool of susceptibles. Over time, even with a
and the next.
very good immunization program in place, accumulation of
In the prevaccine era, measles occurred in very young chil- susceptible children will occur. Clearly, vaccine coverage does
dren and by the age of 5 years almost all had already suffered not equal population immunity.
the disease. With the introduction of the vaccine, and with
increased coverage, the age-specific rate increased to older children. As a consequence, even young adults and adults began Strategies
suffering measles [5].
Given this background, the strategy recommended by the
Pan American Health Organization (PAHO) called for high
vaccination coverage at all times and effective surveillance to
detect measles transmission and respond accordingly. The
100
600
vaccination strategy is three-pronged [6]. First, a one-time500
2 years
80
only ‘catch-up’ campaign, implemented during the low sea400
2 years
son, targets all children 1–14 years of age in an attempt to
60
Incidence
9 years
300
interrupt all chains of measles transmission. This age group
4 years
Coverage
40
4 years
was chosen because it was among this group where more than
200
20
90% of the cases were occurring by the time this program
100
started in the Americas. Second, a ‘keep-up’ component,
0
0
with vaccination in routine services to achieve the highest
coverage possible, is sustained in the new birth cohorts in
Year
every district of every country in order to minimize and delay
the accumulation of susceptibles.
Figure 1. Measles interepidemic periods and vaccination
However, even with high coverage in every district, suscepti*
‡
coverage , Chile, 1960–2007 .
bles
will accumulate because some children will be missed and
*
Vaccination coverage in children less than 1 year of age until 1989
a few that received the vaccine are primary failures, as indiand aged 1 year thereafter.
‡
cated previously. With an average vaccination coverage of
Coverage data not available for 2007.
Source: FCH-IM/Pan American Health Organization.
80%, it is estimated that it takes approximately 4–5 years for
Expert Rev. Vaccines 7(3), (2008)
Feasibility of global measles eradication
Stop the
investigation
No
Health worker suspects
measles or rubella
Yes
Suspected
measles/rubella
case
No
Epidemiological
link to a labconfirmed
case?
Adequate
blood sample
taken?
Yes
Yes
No
Clinically confirmed
Positive serolgy
for IgM antibodies
by capture
test?
No
Laboratory confirmed
Discarded
Figure 3. Surveillance strategy for measles/rubella cases.
the accumulation of susceptible children to be equivalent to
one birth cohort. When this number is reached, a ‘follow-up’
campaign is undertaken in all children aged 1–4 years, regardless of previous vaccination status. This ‘follow-up’ campaign
is designed to address the accumulation of susceptibles. These
campaigns are usually conducted every 4 years and target all
children 1–4 years of age, regardless of previous vaccination
status. This strategy offers children a ‘second opportunity’ to
receive better protection. The first country to utilize this strategy in the Americas was Cuba, which successfully interrupted
measles transmission in the late 1980s (FIGURE 2).
Measles surveillance was designed to be very simple and
timely, as well as sensitive enough to detect all outbreaks. It
needed to be understood by every health worker, allowing for
a prompt and adequate response (FIGURE 3). Briefly, the surveillance strategy works as follows: if a health worker suspects
measles, the suspected case should be visited by a trained epidemiologist who decides whether the case should be classified as a suspected measles case requiring further investigation and collection of a blood specimen for confirmation
through an IgM-capture test. If no adequate specimen was
taken, but there was an epidemiological link with a laboratory-confirmed case, the case also would be laboratory confirmed. Otherwise, it would be clinically confirmed. Clinically confirmed cases are the result of deficiencies in the
surveillance system.
At the beginning of the program, a major proportion of cases
were clinically confirmed, while at present, nearly 100% of
cases are discarded because they have adequate specimens and
negative laboratory results. Surveillance was integrated with
rubella surveillance to maximize the activities related to rubella
www.future-drugs.com
Review
elimination. Now all suspected cases are tested for both measles
and rubella. Performance indicators have been introduced,
including:
• Percentage of sites reporting weekly;
• Percentage of suspected cases with adequate epidemiological
investigation: home visit within 48 h of investigation plus
completeness of relevant data (date of notification, date of
investigation, date of rash onset, date sample taken, type of
rash, presence of fever and dates of previous measles/rubella
vaccinations); and active case-searches;
• Percentage of cases with adequate blood samples;
• Percentage of samples received by the laboratory in less than
5 days;
• Percentage of laboratory results reported in less than 4 days;
• Percentage of cases discarded by laboratory;
• Number of chains of transmission with representative
samples for viral isolation.
For each outbreak, pharyngeal or urine samples are taken
for virus isolation. The proportion of laboratory results available within 5 days of receipt at the laboratory serve to measure
the network performance. An active search for cases is also
conducted periodically in areas that have suffered recent outbreaks or have low coverage, have not reported suspected cases
for some time, or where the population has low access to
health services. Classification of confirmed cases is done by
source of infection as imported, import-related or unknown.
All countries have conducted ‘catch-up’ campaigns with
very high coverage levels and now most of them are implementing ‘follow-up’ campaigns (FIGURE 4). These campaigns
have usually achieved very high coverage, more than 90% at
the national level. Districts that are below 95% coverage are
identified and additional ‘mopping-up’ campaigns are then
implemented in districts at risk.
Surveillance indicators have fluctuated at the regional level
and between countries (FIGURE 5). Laboratory response within
5 days has improved and the laboratory-discarded cases now
reach over 95% [102].
Results
In 1990, there were more than 240,000 cases reported in the
region. In 1996, only 2106 cases of measles were reported in
the Western hemisphere. Of these, some 50% were laboratory
confirmed. By the end of 1996, the number of measles cases
in the Americas had been reduced by 99%, compared with
1990. In 1997, there was a resurgence of measles in São
Paulo, Brazil, the country’s only state that did not implement
a follow-up campaign due in 1996. An outbreak that started
in early 1997, originating from a probable importation from
Europe, spread to other states and to several other countries in
the region. By the end of 1997, more than 50,000 cases were
reported in the Americas, with more than 90% originating in
Brazil [7,8].
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de Quadros, Andrus, Danovaro-Holliday & Castillo-Solórzano
Catch-up campaigns
Confirmed cases (thousands)
250
Cases
Coverage
200
80
60
150
40
100
Follow-up campaigns
20
50
0
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
0
Year
Figure 4. Measles elimination in the Americas, 1980–2007*.
*
Preliminary data – 165 confirmed cases in 2007, coverage data not available.
Routine infant vaccination coverage (%)
100
300
Measles after the interruption of
endemic virus circulation
Since 2003, measles cases in the Americas annually have been reported, following importations from other parts of the
world, at historically low numbers (119
in 2003, 108 in 2004, 85 in 2005, 237
in 2006 and 165 in 2007) (FIGURE 7).
Between 2003 and 2007, besides isolated cases, limited outbreaks have
occurred [12–14,103].
• In 2003–2004, Mexico reported outbreaks totaling 108 cases related to an
H1 virus genotype indigenous to the
Far East but not the Americas. The
most affected age group was individuals aged 20–29 years (36%), followed
by children less than 1 year of age;
• In 2005, Brazil reported an outbreak of
six cases related to an imported case
infected in South Asia related to a D5 virus genotype;
Percentage (%)
In 1998, 14,000 cases were reported following the epidemic
generated in Brazil in 1997, with subsequent spread to Argen- • From November 2005 to February 2006, Canada, Mexico
and the USA reported cases related to a B3 virus genotype, a
tina, Bolivia and, eventually, to the Dominican Republic and
strain indigenous to Central and Western Africa. The 27 cases
Haiti. In 2001, only 545 cases were reported in the entire region,
reported in Mexico were limited to Mexico City. Even though
with epidemic transmission at the end of 2001 only in Venezuela
the source of the outbreak could not be identified, the index
and importations into the northern border areas of Colombia.
case patient was a baggage handler at the international airport;
Transmission in the Dominican Republic and Haiti was interrupted in mid-2001. The majority of cases reported in 2002 were • In May 2006, the USA reported an outbreak of 18 cases in
Boston related to an imported case of likely infection in
from Venezuela, with other countries reporting a few cases
Southeast Asia. The genotype of the virus isolated was D8;
related to importations from other regions of the world [8].
The large measles epidemic that
affected Venezuela between September
2001 and November 2002 is the last
2003
instance of widespread endemic transmis2004
sion of the measles virus in the Americas
2005
100
(FIGURE 6) [8,9]. This outbreak was caused by
2006
2007
an importation of measles virus from
80
Europe. It resulted in 2501 cases (109 in
2001 and 2392 in 2002) reported from 17
60
of the country’s 27 states. Only 18% of
the confirmed cases had been vaccinated
40
with a measles-containing vaccine. This
outbreak spread to Colombia, resulting in
20
140 confirmed cases between January and
September 2002 [10]. The Venezuela out0
break was controlled by mass vaccination
Sites
Timely home Adequate Arrives in lab Results in
Discarded
campaigns targeting individuals aged
reporting visits/adequate samples in 5 days
4 days
by lab
6 months to 14 years nationwide, and
investment
15–34 years in areas considered at risk.
The eradication of the clade 9 of measles Figure 5. Measles surveillance indicators in the Americas, 2003–2007*.
virus that was imported into Venezuela *Data as of 17 January 2008.
Source: FCH-IM/Pan American Health Organization.
has been documented [11].
358
Expert Rev. Vaccines 7(3), (2008)
Feasibility of global measles eradication
Review
Confirmed cases
20
16
12
8
4
0
1 14 27 40 1 14 27 40 1 14 27 40 1 14 27 40 3 16 29 42
2003
2004
2005
2006
2007
Year
250
Confirmed cases
200
Genotype
D4‡
D5
D6
D8
D9
B3
H1
Unknown/other
150
100
D9 transmission
finalized
D6 transmission
finalized
50
0
1
14 27 40 1
2001
14 27 40
2002
1
14 27 40 1
14 27 40
2003
1
2004
14 27 40
1
2005
14 27 40 1
2006
14 27 40
2007
Year
Figure 6. Measles elimination in the Americas, 2001–2007*.
*
Provisional data as of 17 January 2008.
‡
Canadian cases from 2007 (D4 genotype) linked to a case or transmission chain where the source of index case is unknown.
Source: Country reports to FCH/IM. Global Measles Laboratory.
• Between October and December 2006, 57 cases were confirmed in the state of Bahia, Brazil. Seven cases were hospitalized. The measles genotype in this outbreak was D4,
genetically related to a D4 measles virus isolated from four
measles cases that occurred in Canada that year. D4 circulates widely in Europe and Africa, but not in the Americas.
The source of the Brazilian outbreak and the Canadian cases
could not be identified;
• From February 2006 to February 2007, Venezuela reported
122 cases, the primary-case patient was probably exposed to
the measles virus in Spain. Three distinct foci occurred: one
between February and June 2006, with 81 cases distributed in
the Metropolitan District of Caracas, neighboring Carabobo,
Nueva Esparta and Zulia states; the second between November and December 2006, with 12 in Camaguan municipality,
Guarico state; and the third between December 2006 and
February 2007, with 25 cases in Puerto Ayacucho and rural
areas in the Amazonas state. Active case searches for the silent
period between epidemiological weeks 27 and 43 of 2006
identified 14 cases that were classified as clinical measles,
which had not been reported. The virus isolated from these
foci were all B3; the same genotype circulating in Spain;
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• Finally, between April and September 2007, an outbreak in
Quebec, Canada resulted in 95 confirmed cases. Ten cases
required hospitalization. The virus isolated was D4.
A common feature among all import-related outbreaks is that
most cases have either been underimmunized (i.e., one dose of
measles-containing vaccine) or, most frequently, not vaccinated
at all. For example, only four of the 122 cases confirmed in
Venezuela had history of being vaccinated. In Quebec, most of
the 78 individuals without history of receiving a measles-containing vaccine dose opposed vaccination on philosophical
grounds [103].
An accumulation of susceptibles was a contributing factor
that led to the 2006–2007 outbreak in Venezuela, the largest of
all the measles outbreaks occurring in the postelimination era
in the Americas. In Venezuela, the age distribution of the
122 reported cases was 16% in children aged less than 1 year,
32% in individuals aged 1–4 years, 12% in individuals aged
5–17 years and 30% in individuals aged 18–39 years. The last
follow-up campaign was in 2001 and vaccination coverage
reached 93%. However, routine measles, mumps and rubella
coverage in Venezuela had been approximately 80% and, in
most of the outbreak areas, coverage had been particularly low.
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Review
Brazil
Canada
Chile
Costa Rica
Confirmed cases
250
200
150
de Quadros, Andrus, Danovaro-Holliday & Castillo-Solórzano
n = 119
Mexico
USA
Venezuela
n = 237
n = 165
n = 108
n = 85
100
50
0
2003
2004
2005
Year
2006
2007
Figure 7. Distribution of confirmed measles cases in the
Americas, 2003–2007*.
*
Data as of 17 January 2008.
Source: Country reports to FCH-IM/Pan American
Health Organization.
The outbreak started before the follow-up campaign planned
for April 2006. All measles genotypes identified from outbreaks
occurring since 2003 have been nonendemic to the Americas.
Lessons learned
In summary, the ‘catch-up’, ‘keep-up’ and ‘follow-up’ vaccination strategies have been successful in interrupting measles
transmission in the Americas. Campaigns aimed at eliminating
rubella continue to strengthen measles elimination by providing an additional vaccine dose to adolescents and adults. All
countries and territories have been free of indigenous measles
transmission for more than 5 years.
The Americas suffered a re-emergence of measles in
2001–2002 because of failure to fully implement the recommended strategy. In that instance, most cases were seen in vaccinated preschool-aged children and in unvaccinated young
adults, with health professionals playing a very important role
in the chain of transmission. A similar re-emergence of measles occurred in 1997 and 1998 in Brazil for the same reason;
failure to fully implement the strategy.
Although the resurgence of measles in the Americas during
1997 represented an important increase compared with the
number of cases reported in 1996, the total of 53,000 cases
represents only approximately 10% of the cases reported in
1990. Nevertheless, important lessons can be extracted from
this experience.
First, the lack of a timely ‘follow-up’ vaccination campaign
in 1996 in São Paulo for children 1–4 years of age, combined
with low coverage of routine vaccination (‘keep-up’) of infants
with at least one dose of measles vaccine, allowed for a fast
and dangerous accumulation of susceptible children. Second,
the presence of young adults who were not exposed to the
natural infection and had never been vaccinated exacerbated
the risk of an outbreak. Third, the measles virus was most
360
likely introduced from Europe into São Paulo. Finally, the
city’s great population density facilitated contact between
infected individuals and the susceptible population.
However, since 2003, importations of measles into countries
that have followed the PAHO recommended strategies have not
generated sustained epidemics. In most instances, the outbreaks
have been quickly controlled. Surveillance data for measles,
combined with the results of molecular epidemiology studies,
indicate that the countries of the Americas are continually
exposed to the measles virus from other regions of the world
where measles continues to be endemic.
For the early detection of imported cases, recent outbreaks
have illustrated that it is necessary to include private-sector
health facilities that care for tourists and intercontinental
travelers in the surveillance system. In addition, door-to-door
and active case searches for additional cases once an importation has been identified have proven essential for defining the
size and extent of the outbreak and to tailor the strategies
required to control it. In the Dominican Republic and Haiti
there were door-to-door vaccinations to control a vaccinederived polio outbreak that occurred in 2000–2001. This
polio outbreak was concomitant with the importation of measles into both countries; therefore, the vaccination campaigns
used polio and measles vaccines. Furthermore, health workers
were offered a US$100 reward if they found a case of polio or
measles during the house-to-house visits. No case of either
disease was found.
Measles importation should result in significant efforts to
trace all contacts. For example, the initial case of a six-person
outbreak reported in Brazil in 2005 was exposed to a confirmed
measles outbreak in the Maldives during a surfing tournament.
During the periods of incubation and communicability, this
person traveled by air on international flights before arriving in
Brazil and traveled on five domestic flights within Brazil. Two
secondary infections among fellow passengers traveling
between São Paulo and Florianópolis were confirmed by viral
isolation and serology. Of the 334 passengers traveling with this
index passenger during his period of communicability, 118
were contacted and investigated. No other secondary cases were
identified [13]. In 2007, three examples of active international
follow-up of measles contacts occurred. A student from India
came down with measles during an international student fair in
New Mexico. Contacts were swiftly followed in eight countries
of the Americas. The second instance occurred when 14 individuals from Latin America and the Caribbean were exposed to
measles in Quebec, Canada, after one of the confirmed measles
cases attended an event, potentially exposing over 800 international participants. Finally, one of the participants of the ‘Little
League World Series’ tournament held in Williamsport, Pennsylvania, USA, was diagnosed with measles. The infected player
had traveled from Japan where he was exposed to the measles
prior to his departure for the USA. Four international teams
from the region were participating in the event. No secondary
case resulted in the region from any of these events.
Expert Rev. Vaccines 7(3), (2008)
Feasibility of global measles eradication
Review
To prevent importations, the PAHO issued an epidemiological alert to individuals of the Western hemisphere attending the
FIFA World Cup in Germany in 2006, where a measles outbreak was occurring at the time [14]. Similarly, the Caribbean
countries hosting the Cricket World Cup in 2007 issued an
alert to strengthen surveillance and advise visitors to be vaccinated [15]. Another alert was issued for those participating in
the Pan-American Soccer Cup (Copa America) in Venezuela in
2007, when the measles outbreak was ongoing. Such special
global alerts have helped the region of the Americas maintain
its status of measles elimination.
measles should be a good investment to avoid expensive epidemics of measles but, most importantly, to save the almost
300,000 children who die every year due to infection with the
measles virus.
However, before a global initiative on measles eradication is
launched, it is necessary to demonstrate that poliomyelitis has
been eradicated. There also will be programmatic, political and
financial obstacles that will need to be overcome before global
measles eradication is launched. Partnerships will be essential to
support governments embarking on it. It is not only a dream to
imagine a world free of measles by the year 2015.
Expert commentary & five-year view
Financial & competing interests disclosure
The experience of the last 5 years with the measles eradication
program in the Americas shows that measles transmission can
be interrupted and interruption can be sustained over a long
period if countries fully apply the approriate strategies of vaccination and active, integrated surveillance of measles and
rubella, as recommended by the PAHO for all the countries of
the Americas.
The experience described indicates that the PAHO strategy
can effectively achieve and sustain the interruption of epidemic
transmission in a very large geographical area, such as the Western hemisphere. From this experience, we believe that global
eradication is feasible if the appropriate strategies are implemented. The current measles vaccine, with 95% vaccine efficacy, has been adequate to stop endemic measles transmission
when used in the recommended strategies of catch-up, keep-up
and follow-up, as described previously. The eradication of measles will have a major impact in childhood morbidity and mortality. Even in a new paradigm on which eradication is not followed by the discontinuation of vaccination, eradication of
The authors have no relevant affiliations or financial involvement with
any organization or entity with a financial interest in or financial conflict
with the subject matter or materials discussed in the manuscript. This
includes employment, consultancies, honoraria, stock ownership or options,
expert testimony, grants or patents received or pending, or royalties.
No writing assistance was utilized in the production of this manuscript.
2
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www.future-drugs.com
• Measles is no longer an endemic disease in the Americas and
interruption of transmission has been documented in
most countries.
• As of December 2007, 5 years have elapsed since the detection
of the last endemic case in Venezuela in November 2002.
• This experience demonstrates that interruption of measles
transmission can be achieved and sustained over a long period
of time.
• Global eradication should be feasible if the appropriate
strategies are implemented.
6
de Quadros CA, Olivé JM, Hersh BS et al.
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Websites
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assessment and monitoring. WHO vaccinepreventable diseases: monitoring system,
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www.who.int/immunization_monitoring/
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Affiliations
•
Ciro A de Quadros
Executive Vice-President, Sabin Vaccine
Institute, Washington, DC 20006, USA
Tel.: +1 202 265 6515
[email protected]
•
Jon Kim Andrus
Lead Technical Advisor, Immunization
Unit, Pan American Health Organization,
Washington, DC, USA
•
M Carolina Danovaro-Holliday
Technical Officer, Immunization Unit,
Pan American Health Organization,
Washington, DC, USA
•
Carlos Castillo-Solórzano
Regional Advisor, Immunization Unit,
Pan American Health Organization,
Washington, DC, USA
Expert Rev. Vaccines 7(3), (2008)