These guidelines were prepared by the technical divisions of the Pan American Health Organization.
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Vaccinations in Disaster Situations:
Recommendations of the PAHO/WHO Special Program for Vaccines and Immunization

  1. Ensure that all displaced people and/or people in shelters (adults and children), including health workers in the shelters, are vaccinated against measles. It is necessary to prepare a list of needs to search for and mobilize resources.
  2. Maintain routine vaccination with the basic vaccination schedule, since a reduction in coverage in the medium-term could result in a resurgence of vaccine-preventable diseases that have already been controlled and/or eradicated, such as measles, polio, whooping cough, diphtheria, and neonatal tetanus.
  3. Evaluate damage to the cold chain and the loss of biologicals, syringes and supplies.
  4. Immediately re-stock vaccines utilized routinely by the national immunization programs.
  5. Implement the temporary use of cold boxes (RCW42) to ensure the conservation of vaccines in the affected areas and their distribution, provided that there is ice available.
  6. Implement the use of photovoltaic refrigerators for vaccine storage and ice production, guaranteeing sufficient batteries.
  7. Initiate recovery of the cold chain (purchase of refrigerators, thermos, thermometers, etc.)

Overcrowding and poor water and sanitation favor an increase in the incidence of diarrheal diseases (associated with sanitation and water quality) and respiratory diseases (overcrowding). Mass immunization during situations of natural disasters is counterproductive and diverts limited human resources and materials from other more effective and urgent measures. Immunization campaigns can give a false sense of security, leading to the neglect of basic measures of hygiene and sanitation, which are more important during the emergency.

Mass vaccination would be justified only when the recommended sanitary measures do not have an effect and if there is evidence of the progressive increase in the number of cases with the risk of an epidemic. A vaccine with the following characteristics could be considered useful in this situation:

  • A vaccine of proven efficacy, high safety and low reactogenicity
  • A vaccine that is easy to apply (single-dose)
  • A vaccine that confers rapid and long-lasting protection for people of all ages.
  • Sufficient quantities of vaccine should be available to guarantee the supply for the entire population at risk.
  • Low-cost vaccines.

Regarding questions on the possible use and demand during an emergency for vaccines that are not included in national immunization programs, it is important to recognize the costs and mobilization efforts needed to carry out a mass immunization. The vaccines frequently proposed are those against cholera, typhoid fever, and meningococcal meningitis. Other vaccines that have recently been licensed have also been suggested, such as rotavirus, hepatitis A, Haemophius influenzae type b and chickenpox. Below is a summary of the vaccines in question:

  • Cholera vaccine: The traditional vaccine against cholera (killed whole-cell) presents low efficacy and high reactogenicity, and as a result, is not recommended for epidemic control. New vaccines that may be considered for use include a killed whole-cell vaccine supplemented with recombinant subunit B of the cholera toxin and an attenuated oral vaccine. Existing information for the first vaccine indicates that two doses administered with a two-week interval to the population over 1 year of age will reduce the number of cases during a cholera epidemic, but it will not eliminate the probability of an epidemic occurring in the two years following vaccination. This is due to the rapid decrease of protection over time. In children under 5, protection disappears after 6 months. For the live, attenuated vaccine, there is no information available at this time to support its use.

  • Typhoid fever vaccine: The traditional vaccine against typhoid fever (killed whole-cell) presents low efficacy and high reactogenicity, and as a result is not recommended for epidemic control. The live, attenuated, oral vaccine requires of four doses, administered in a strict regimen, which requires special infrastructure (the vaccine is very heat labile and requires refrigeration). The polysaccharide vaccine is effective only in populations over two years of age.

  • Rotavirus vaccine: This is a recently licensed vaccine in the United States. Field studies have demonstrated its effectiveness in preventing severe cases of the disease (diarrheal diseases with dehydration), thus reducing the need for hospitalization. Three doses of vaccine are required with at least one-month intervals. The effectiveness of this vaccine has not been verified in emergencies, it is expensive, and there is limited availability.

  • Haemophilus influenzae type b vaccine: This vaccine has had a significant impact on meningitis, pneumonia and other invasive forms of the disease, once introduced into routine immunization programs. The disease is not epidemic and as a result is not considered a problem in disaster situations. The disease occurs in children under 2 years of age, and to induce protection at least 2 doses are required with a minimum interval of 1 month. PAHO promotes the introduction of this vaccine into routine immunization programs, but the sustainability of the vaccine supply should be assured.

  • Meningococcal vaccines: These vaccines have been used to control meningococcal meningitis due to Groups A and C in epidemic emergencies. Once epidemiological surveillance determines an increase in incidence and identifies the responsible serogroup (A and/or C), age group, and affected area or region, then vaccination can be considered. A stock of meningococcal vaccine should be established in order to ensure immediate availability for outbreak control if needed. Vaccination during non-epidemic periods is not considered to be an effective measure because of the short duration of immunity in the infant population.

  • Hepatitis A vaccine: In Central America, infection with the hepatitis A virus occurs at an early age. Recent data show that in Nicaragua, children from 2 to 4 years of age present a seroprevalence of 73%. Pathogenicity varies with age and is more serious in adults. In children under 6 years, infection is asymptomatic (greater than 70%). The vaccine is expensive and two doses are applied in children over 2 years of age, which means that its use is not justified in emergencies.

  • Chickenpox vaccine: There is no recommendation for the use of chickenpox vaccine in disaster situations.

 

Contact
Peter Carrasco
PAHO/WHO Special Program for Vaccines and Immunization
Email: carrascp@paho.org