Ciro A. de Quadros

Evolution of Streptococcus pneumoniae serotypes and penicillin susceptibility in Latin America, Sireva-Vigía Group, 1993 to 1999

BACKGROUND Since 1993 the Pan American Health Organization has coordinated a surveillance network with the National Reference Laboratories of Argentina, Brazil, Chile, Colombia, Mexico and Uruguay aimed at monitoring capsular types and antimicrobial susceptibility of Streptococcus pneumoniae causing invasive disease in children <6 years of age. METHODS The surveillance system included children 6 years of age and younger with invasive disease caused by S. pneumoniae. The identification, capsular typing and susceptibility to penicillin of the isolates were conducted using a common protocol, based on standard methodologies. RESULTS By June, 1999, 4,105 invasive pneumococcal isolates had been collected mainly from pneumonia (44.1%) and meningitis (41.1%) cases. Thirteen capsular types accounting for 86.1% of the isolates (14, 6A/6B, 5, 1, 23F, 19F, 18C, 19A, 9V, 7F, 3, 9N and 4) remained the most common types during the surveillance period. Diminished susceptibility to penicillin was detected in 28.6% of the isolates, 17.3% with intermediate and 11.3% with high level resistance. Resistance varied among countries and increased during this period in Argentina, Colombia and Uruguay. Serotypes 14 and 23F accounted for 66.6% of the resistance. CONCLUSION These surveillance data clearly demonstrate the potential impact of the introduction of a conjugate vaccine on pneumococcal disease and the need for more judicious use of antibiotics to slow or reverse the development of antimicrobial resistance.Background. Since 1993 the Pan American Health Organization has coordinated a surveillance network with the National Reference Laboratories of Argentina, Brazil, Chile, Colombia, Mexico and Uruguay aimed at monitoring capsular types and antimicrobial susceptibility of Streptococcus pneumoniae causing invasive disease in children <6 years of age. Methods. The surveillance system included children 6 years of age and younger with invasive disease caused by S. pneumoniae. The identification, capsular typing and susceptibility to penicillin of the isolates were conducted using a common protocol, based on standard methodologies. Results. By June, 1999, 4105 invasive pneumococcal isolates had been collected mainly from pneumonia (44.1%) and meningitis (41.1%) cases. Thirteen capsular types accounting for 86.1% of the isolates (14, 6A/6B, 5, 1, 23F, 19F, 18C, 19A, 9V, 7F, 3, 9N and 4) remained the most common types during the surveillance period. Diminished susceptibility to penicillin was detected in 28.6% of the isolates, 17.3% with intermediate and 11.3% with high level resistance. Resistance varied among countries and increased during this period in Argentina, Colombia and Uruguay. Serotypes 14 and 23F accounted for 66.6% of the resistance. Conclusion. These surveillance data clearly demonstrate the potential impact of the introduction of a conjugate vaccine on pneumococcal disease and the need for more judicious use of antibiotics to slow or reverse the development of antimicrobial resistance.

Eradication of poliomyelitis: progress in the Americas.

In the span of 5 years since the eradication initiative was launched and only 3 years since external funds were made available, PAHO has been able to develop and implement a comprehensive program strategy for polio eradication that includes the following components: achievement and maintenance of high immunization levels (which include the supplemental strategies of national immunization days and mop-up operations); effective surveillance to detect all new cases; and a rapid response to the occurrence of new cases. Despite yearly increases in the number of cases of acute flaccid paralysis reported to the surveillance system, a decline in reported confirmed cases of polio has occurred since 1986 to record low levels in 1989. Cases in 1989 were reported from only 0.7% of the counties in the Americas. The occurrence of 24 wild-type virus isolates in 1989 were limited to only three geographic areas: northwestern Mexico; the northern Andean Region; and northeastern Brazil. At this writing the clock is ticking with only 3 months left to achieve the goal of interrupting transmission by the end of 1990. If the current level of effort is sustained and special efforts are directed at the remaining foci of infection, the eradication of the transmission of wild-type poliovirus from the Americas can be achieved. Continued external financial support will be critical if the effort is to succeed. The prospect of poliomyelitis eradication in the Americas led the 41st World Health Assembly of WHO to adopt a resolution in May, 1988, to eradicate the indigenous transmission of wild-type poliovirus from the world by the year 2000.(ABSTRACT TRUNCATED AT 250 WORDS)

Review of regional measles surveillance data in the Americas, 1996-99.

BACKGROUND In 1994, ministers of health of countries of North and South America established the goal of measles eradication from the western hemisphere by 2000. To accomplish this goal, the Pan American Health Organization (PAHO) developed an enhanced measles vaccination strategy. METHODS PAHOs measles eradication vaccination strategy has evolved into three principal components; a catch-up measles vaccination campaign, maintenance of high vaccination coverage (keep-up), and periodic follow-up measles vaccination campaigns. To monitor progress towards measles eradication, measles surveillance has been strengthened, including the laboratory investigation of suspected measles cases. FINDINGS Both the catch-up and follow-up mass campaigns achieved high vaccination coverages in the respective targeted age groups. In 1996, only 2109 confirmed measles cases were reported in the Americas. In 1997, there was a resurgence of measles in the Americas, mostly as a result of a large measles outbreak with over 42000 cases, which occurred mainly among unvaccinated young adults in Sao Paulo State, Brazil. By 1998, there was a reduction in the number of reported confirmed measles cases, with a total of 14474 cases. Reduction of cases continued to the end of 1999, with a total of only 2828 confirmed cases. INTERPRETATION PAHOs measles eradication strategy has been effective in interrupting transmission and maintaining the absence of measles virus circulation in most parts of the Americas. The PAHO experience provides strong evidence that with full implementation of an appropriate vaccination strategy, measles transmission can be effectively interrupted.

New Horizons in the Control of Rubella and Prevention of Congenital Rubella Syndrome in the Americas

Data from the regional measles surveillance system have documented widespread rubella virus circulation in many different countries in the Americas. In response to the ongoing endemic incidence of the disease and the potential for a major rubella epidemics in the region, the Pan American Health Organization Technical Advisory Group on Vaccine Preventable Diseases recommended the implementation of a regional initiative to strengthen rubella and congenital rubella syndrome (CRS) preventive efforts in 1997. This article summarizes and highlights the progress toward accelerated rubella control and CRS prevention in the English-speaking Caribbean and in Chile, Costa Rica, and Brazil. Useful knowledge is being generated for the adaptation of similar rubella strategies elsewhere. The findings also document the feasibility of implementing the recommended strategies and their rapid impact on disease burden.

Measles eradication in the Americas: progress to date.

The region of the Americas has shown extraordinary progress in its fight to interrupt measles transmission. The Pan American Health Organizations recommended strategy includes the following: a 1-time nationwide campaign targeting 1- to 14-year-old children; routine vaccination among 1-year-olds; and nationwide campaigns conducted every 4 years, targeting all 1- to 4-year-olds. Rapid house-to-house monitoring of vaccination and measles surveillance are other essential components of the strategy. During 2001, only 541 cases were confirmed in the region. In 2002, only Venezuela and Colombia had indigenous transmission. After important vaccination efforts in both countries, the last reported case occurred on 20 September 2002, in Venezuela. Since then, no confirmation exists of indigenous measles circulation anywhere else in the region. Nonetheless, important challenges remain, including insufficient coverage during routine and campaign vaccination and inadequate investigation of some cases.

The future of immunisation policy, implementation, and financing

Vaccines have already saved many lives and they have the potential to save many more as increasingly elaborate technologies deliver new and effective vaccines against both infectious diseases--for which there are currently no effective licensed vaccines--such as malaria, tuberculosis, and HIV and non-infectious diseases such as hypertension and diabetes. However, these new vaccines are likely to be more complex and expensive than those that have been used so effectively in the past, and they could have a multifaceted effect on the disease that they are designed to prevent, as has already been seen with pneumococcal conjugate vaccines. Deciding which new vaccines a country should invest in requires not only sound advice from international organisations such as WHO but also a well informed national immunisation advisory committee with access to appropriate data for local disease burden. Introduction of vaccines might need modification of immunisation schedules and delivery procedures. Novel methods are needed to finance the increasing number of new vaccines that have the potential to save lives in countries that are too poor to afford them. Here, we discuss some options.

Progress toward Measles Eradication in the Region of the Americas

Since 1994, when the goal of interrupting indigenous measles transmission was adopted, important progress has been made toward the control of measles in the Americas. Thirty-nine (95%) of 41 countries reporting to the Pan American Health Organization (PAHO) conducted catch-up vaccination campaigns during 1989-1995 and follow-up measles campaigns every 4 years. Routine (keep-up) vaccination coverage in the Region increased from 80% in 1994 to 94% in 2000. Measles vaccination coverage ranged between 75% and 99% in 2000 and between 53% and 99% in 2001. As a result, in 2001, the total number of confirmed measles cases reached a record low of 537, 99% lower than the number reported in 1990. In 2002, only Venezuela and Colombia had known indigenous transmission. As of January 2003, no known indigenous measles transmission had occurred in the Region since November 2002. This is due to high political commitment and implementation of PAHOs recommendations, including strengthened supervision and monitoring to improve accountability at the local level.

Measles vaccination and Guillain-Barré syndrome

BACKGROUND Guillain-Barré syndrome (GBS) has been associated with several infectious agents, and the possibility that the disorder may be caused by vaccination has been raised. We compared the numbers of cases of GBS observed immediately after mass measles vaccination campaigns with the numbers that would be expected from baseline rates, to assess whether there is a causal relation between measles vaccination and GBS. METHODS We analysed data on 2296 cases of GBS reported to the Poliomyelitis Eradication Surveillance System of the Pan American Health Organization as cases of suspected poliomyelitis. These cases occurred among 73 million immunised children aged 9 months to 15 years in Argentina, Brazil, Chile, and Colombia, between January, 1990, and December, 1994. These children were targeted for mass measles vaccination campaigns (each lasting 1 month) in 1992 and 1993. The frequency of GBS cases observed during the vaccination campaigns or the next 42 days (the latent period) was compared with that during the rest of the study period, with the assumption of a Poisson distribution. FINDINGS The average annual incidence of GBS was 0.62 per 100000 children aged 1-14 years. The number of cases that would be expected within any 72-day period would therefore be 92. The average observed number of cases during latent periods after measles vaccination was 97. The probability that 97 or more cases would occur during a period with an expected number of 92 was 0.31. INTERPRETATION The average annual rates of GBS by age-group for the 5 years analysed were consistent with previous data; thus we are confident that the surveillance system is sufficiently sensitive. There was no statistically significant association between measles vaccination and GBS. If there is any causal relation, the number of GBS cases due to measles vaccination was so small that data from the vaccination of more than 70 million children were not sufficient to detect a rise in the number of observed GBS cases beyond the expected number.

The burden of pneumococcal disease among Latin American and Caribbean children: review of the evidence

OBJECTIVE To conduct a comprehensive review of data on pneumococcal disease incidence in Latin America and the Caribbean and project the annual number of pneumococcal disease episodes and deaths among children < 5 years of age in the region. METHODS We carried out a systematic review (1990 to 2006) on the burden of pneumococcal disease in children < 5 years of age in the region. We summarized annual incidence rates and case fatality ratios using medians and interquartile ranges for invasive pneumococcal disease (IPD) (including all-IPD and separately abstracting pneumococcal meningitis, pneumonia, bacteremia, and sepsis data), pneumonia (all cause and radiologically confirmed), and acute otitis media by age group: < 1 year, < 2 years, and < 5 years. We modeled age-specific cumulative incidence of disease obtained from standard Kaplan-Meier analysis and projected data to obtain regional estimates of disease burden. We adjusted burden estimates by serotype coverage, vaccination coverage, and vaccine efficacy to estimate the number of cases and deaths averted. RESULTS Of 5 998 citations identified, 26 papers from 10 countries were included. The estimated annual burden of pneumonia, meningitis, and acute otitis media caused by pneumococcus in children < 5 years of age ranged from 980 000 to 1 500 000, 2 600 to 6 800, and 980 000 to 1 500 000, respectively. An estimated 12 000 to 28 000 deaths due to pneumococcal disease occur in the region annually. Pneumococcal conjugate vaccine could save 1 life per 1 100 and prevent 1 case per 13 children vaccinated. CONCLUSION A substantial burden of pneumococcal disease in the region is potentially preventable with pneumococcal conjugate vaccines and should be considered in regional vaccine decision making. Results are limited by the very few studies, conducted in selected settings, included in this review.

Feasibility of global measles eradication after interruption of transmission in the Americas

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.