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INTRODUCTION OF Haemophilus influenzae type b
VACCINE IN THE AMERICAS

In 1994, Uruguay decided to include Hib vaccine in their regular immunization program. The decision was made based on the information available on meningeal diseases from the meningitis surveillance system implemented years before in the country, together with the need for an immediate response to the increasing awareness of these diseases among concerned parents and the medical profession. Under almost similar circumstances, in 1996, Chile introduced Hib vaccine. The introduction was facilitated by the fact that several clinical trials with these vaccines had been conducted in the country and the health authorities were aware of their safety, efficacy and effectiveness. Two different strategies were followed in both countries mainly because the inclusion of Hib vaccine meant an increased cost to the immunization programs. Uruguay vaccinated all the children under the age of four years, indicating three doses for the children under 6 months of age, two doses for the children between 7 months and one year of age, and one dose for the children above one year of age. A booster dose was also given to the children after one year of age. Chile vaccinated the children at 2, 4 and 6 months of age instead, without a booster. The strategy used in Uruguay showed an almost immediate impact on Hib disease. In Chile, the impact took a longer time to be observed, although tendencies to the decrease in incidence were noticed within the first year.

Impact of Hib vaccination in Uruguay and Chile

By the end of 1996, the Special Program for Vaccines and Immunization (SVI) decided to have a more active involvement in promoting the surveillance of Hib disease as well as evaluating the possible introduction of the vaccine in the regional regular immunization programs. The decision was reinforced by results from clinical studies with Hib vaccine in the Gambia that indicated the pathogen can be responsible for up to 20% of radiologically confirmed pneumonia. Relevant information regarding the vaccine and the disease was distributed to the countries through the SVI staff members in the field, articles on Hib vaccine and disease were published in the EPI newsletter and the subject was presented at regional and sub-regional program meetings. Parallel to this promotional activity, an epidemiological surveillance network organized to monitor invasive pneumococcal disease in children under the age of 5 years in six countries of the region also strengthened the surveillance on Haemophilus influenzae. At this time, 30% of all newborns in the Region had Hib vaccine as part of their regular immunization schedule, but only 3.4% of all newborns in Latin America and the Caribbean Region.

Situation in 1996

In 1997, two major decisions were made by PAHO. One at the level of PAHO's Directing Council which urged the Member States, among other things, to strengthen surveillance in preparation for the introduction of new vaccines (such as Haemophilus influenzae type b, hepatitis B and measles/mumps/rubella) to accurately determine disease burden and develop appropriate vaccination strategy. The second, done by the Technical Advisory Group at the XII TAG meeting in Guatemala, in September 1997. At that time the TAG recommended:

  1. the use of Hib vaccine in the regular immunization programs;
  2. the establishment of well structured surveillance systems to monitor illnesses due to Hib and measure impact;
  3. the use of the PAHO Revolving Fund for joint purchase of vaccine, and
  4. careful evaluation of other vaccination strategies (reduced dose or reduced number of doses).

By 1998, more countries had integrated Hib vaccine in the immunization program: Argentina, Colombia, Costa Rica, Cayman Island, Netherland Antilles, Aruba, British Virgin Islands, Bermuda, Bahamas, Antigua and Barbuda, Anguilla, Guadaloupe and Martinique. The Social Security of Mexico was vaccinating its children and Peru used a special vaccination strategy by which the socioeconomic strata I and II were vaccinated. This accounted for 48% of the newborns in the whole region and 29% of the newborns in Latin America and the Caribbean having Hib vaccine as part of their immunization schedule.


IMPROVED SURVEILLANCE

Since the TAG meeting, SVI has taken some important actions to strengthen the surveillance system initiated for S. pneumoniae. At a meeting in Managua, Nicaragua in February 1998 with the participation of epidemiologists and laboratory personnel from Central America, a generic protocol was developed for the surveillance of bacterial pneumonia and meningitis. The final model for this surveillance system is the organization of a network of sentinel hospitals in the region that will be monitoring diseases due to H. influenzae, and S. pneumoniae and at a later stage will include N. meningitidis. In order to standardize the microbiological procedures followed by the public health laboratories, a series of training workshops were conducted which rely principally in the concept of training the trainers. The methodology and manuals, initially harmonized by the initial countries together with the Canadian laboratory partner, were later transferred to the public health laboratories of the newly participating countries and further transferred to the hospitals. A quality control system was developed to assure the consistency and quality of the laboratory results.

In order to measure and evaluate the possible impact of Hib vaccine on respiratory infections (pneumonia), a protocol to conduct case-control studies is being finalized. Once completed, the protocol will be implemented in some of the countries that have introduced the Hib vaccine recently.


PAHO REVOLVING FUND

Until 1998, most of the countries using Hib vaccine were purchasing it directly from the manufacturers and paying prices that ranged between US$4.00 to US$8.50, although prices were decreasing with the years. The number of doses purchased through the Revolving Fund was very low and the prices were similar to what the countries were paying until the demand for vaccine increased with the inclusion of Brazil and Mexico requests through the PAHO Revolving Fund. The volume of vaccine required dropped the price of vaccine dramatically to the low of US$2.18 for the liquid formulation and US$2.60 for the freeze-dried formulation. A combined vaccine is also available that includes five antigens: tetanus, diphtheria, pertussis, hepatitis B and Hib at a price of US$3.50. This vaccine can have a major impact in the vaccination programs as one injection administers the five antigens simultaneously, thus reducing the cost of delivery, the number of injections and may help vaccination compliance and coverage. The volume of demand for the vaccine generated by Brazil and Mexico resulted in a more affordable vaccine for other countries.


FINANCING OF THE Hib VACCINE

In general, the resources used for the purchase of Hib vaccine by the countries were assigned by the Ministry of Health in their yearly budget as is the case for Uruguay, Chile, Argentina, Brazil, Mexico, Costa Rica and Honduras among others. These budgets are protected and guaranteed by laws or presidential decrees in some of the countries. Peru also assigned the resources from the regular budget but for the purchase of vaccine for the lower socioeconomic strata (strata I and II).

Other forms of resources can be exemplified by the cases of Mexico, where the Social Security used its budget to purchase vaccine for its population, or Colombia, where the money was pooled from the Ministry of Health and health promoters.

At the moment, there are ongoing negotiations between the World Bank and Bolivia, with the technical cooperation of PAHO, to include resources for the introduction of vaccines in the loan negotiations.

There are also negotiations for donation/purchase agreements by which a country would receive a donation of vaccine to immunize the birth cohort during the first year with the compromise of purchasing increasing percentages of vaccine in the coming years until completing country requirements.

Since the TAG meeting in 1997, at every sub-regional meeting that was conducted: the Southern Cone, Bolivia and Brazil, the Andean Region and Brazil, Central America, Dominican Republic, Cuba and Mexico, and the Caribbean Countries, introduction of Hib vaccine was one of the subjects discussed. At each meeting, the overall situation was presented and countries that were introducing the vaccine or considering the introduction had an opportunity of presenting their individual cases. This has probably been one of the most important incentives for promoting Hib vaccine in the Region, which translates into the fact that by 1999 over 80% of the newborns will have Hib vaccine as part of their immunization schedule.


Why has the introduction of Hib vaccine been so successful in the Americas and what can we learn for future new vaccines?

The Region of the Americas is characterized by having strong EPI programs in the countries supported intensively by a dedicated program in the Pan American Health Organization. This commitment to immunization, manifested by the recognition of vaccines as a public good and one of the most cost-effective interventions in health care, has lead the Region to be the first in eradicating polio, and moving quickly into eliminating measles. This high awareness has been demonstrated once more by the rapid uptake of this new vaccine.

The availability of safe and effective vaccines against Hib meningitis and the knowledge of their existence have facilitated the decision making process of introducing this vaccine in the countries, as the severity of meningitides and their sequelea have always been a great concern of health professionals and parents. PAHO has taken a leading role in promoting the use of the vaccine, as well as the establishment of surveillance systems to evaluate the burden of disease and monitor the impact of vaccine utilization. This PAHO promotion has occurred through staff members in the countries, the EPI newsletter, and at the program regional and subregional meetings. The fact that staff members could provide answers in an efficient and rapid manner to questions related to quality, specifications, characteristics, formulations, and use of the Hib vaccines was extremely important for the visibility and involvement of PAHO. This culminated with the PAHO's Directing Council Resolution in 1997 regarding Hib vaccine introduction and surveillance. It was of great importance that two countries in the region, Uruguay in 1994 and Chile in 1996, had introduced the vaccine; these were regional examples for the other countries of the use and impact of the vaccine in the regular immunization program.

One of the principal deterrents for introduction of the vaccine has been the cost, although prices have been steadily dropping. Recently, with the consolidation of Hib vaccine demand, added to the decision of Brazil and Mexico to purchase Hib vaccine via the PAHO Revolving Fund, prices have dropped to a low level. These new prices are allowing other countries make the decision to use the vaccine in their regular immunization programs. Utilization of the new formulations like the combined pentavalent vaccine (DTP-HepB + Hib) will have an important impact on the prices of the monovalent Hib and DTP-Hib combined vaccines due to competition.

The reasons behind the success of Hib vaccine introduction in the Region can be attributed to the existence of strong EPI programs in the countries together with strong leadership at PAHO central and country level.

This example should be followed for future introduction of vaccines such as the pneumococcal conjugate vaccines, rotavirus or other vaccines of regional importance. The countries in the region must start collecting epidemiological data, strengthening the surveillance systems for these vaccine preventable diseases and raising awareness of the diseases and their burden. Staff from the Division of Vaccine and Immunization (HVP) at PAHO headquarters and in the region must be proactive in following vaccine developments, results from clinical trials, and collecting information on vaccine characteristics, formulations, and use. This will facilitate future support to the Ministry of Health whenever they will be ready to consider the introduction of new vaccines.


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