Minimum time interval adjustment for 4-3-1 immunization rates among two-year-old children

Evaluation of invalid vaccine doses in 31 countries of the WHO African Region

We examined (a) the fraction of and extent to which vaccinations were administered earlier than recommended (age-invalid) or with too short intervals between vaccine doses (interval-invalid) in countries of the World Health Organisation (WHO) African Region and (b) individual- and community-level factors associated with invalid vaccinations using multilevel techniques. Data from the Demographic and Health Surveys conducted in the last 10 years in 31 countries were used. Information about childhood vaccinations was based on vaccination records (n=134,442). Invalid vaccinations (diphtheria, tetanus, pertussis [DTP1, DTP3] and measles-containing vaccine (MCV)) were defined using the WHO criteria. The median percentages of invalid DTP1, DTP3 and MCV vaccinations across all countries were 12.1% (interquartile range, 9.4-15.2%), 5.7% (5.0-7.6%), and 15.5% (10.0-18.1%), respectively. Of the invalid DTP1 vaccinations, 7.4% and 5.5% were administered at child's age of less than one and two weeks, respectively. In 12 countries, the proportion of invalid DTP3 vaccinations administered with an interval of less than two weeks before the preceding dose varied between 30% and 50%. In 13 countries, the proportion of MCV doses administered at child's age of less than six months varied between 20% and 45%. Community-level variables explained part of the variation in invalid vaccinations. Invalid vaccinations are common in African countries. Timing of childhood vaccinations should be improved to ensure an optimal protection against vaccine-preventable infections and to avoid unnecessary wastage in these economically deprived countries.

Related factors of age-appropriate immunization among urban-rural children aged 24-35 months in a 2005 population-based survey in Nonsan, Korea

PURPOSE

This study was aimed to determine the status and related factors of age-appropriate immunization among urban-rural children aged 24-35 months in a 2005 population-based survey in Nonsan, Korea.

MATERIALS AND METHODS

We conducted household survey and provider check using questionnaire and checklist to obtain data on immunization status for children, aged 24-35 months. Age-appropriate immunization was defined as status of receiving the fourth diphtheria-tetanus-pertussis (4 DTP), 3 Polio, the first measles-mumps-rubella (1 MMR) doses, and the 4 : 3 : 1 series.

RESULTS

Age-appropriate immunization rates were 51.7% for 4 DPT, 88.0% for 3 Polio, 87.9% for 1 MMR, and 50.3% for the 4 : 3 : 1 series. First-born children, lower perceived barrier scores, and higher perception of immunization data were significantly related to age-appropriate immunization.

CONCLUSION

The findings indicated that age-appropriate immunization rate could be improved by implementing reminder/recall service and providing the knowledge about immunization. Identification and consideration related factors would improve immunization rate and age-appropriate immunization.

Evaluation of invalid vaccine doses

BACKGROUND

The 2002 Recommended Childhood Immunization Schedule clarified the definition of an invalid dose of vaccine as any dose administered >/=5 days before the minimum age or interval had elapsed. Any invalid dose of vaccine should be repeated.

OBJECTIVE

Determine the proportion of U.S. children who received an invalid dose of vaccine, evaluate the impact on vaccination coverage levels if invalid doses were not counted, and determine the vaccine purchase cost if at least one invalid dose is repeated.

METHODS

Provider-reported vaccination histories of children aged 19 to 35 months sampled by the 2000 National Immunization Survey were evaluated. Analyses were performed in 2002 after the 2002 Advisory Committee on Immunization Practices (ACIP) Recommended Immunization Schedule was released. Any vaccine dose administered >/=5 days before the recommended minimum age or interval was classified as invalid. Change in vaccination coverage was determined by subtracting estimated valid-dose coverage (based on number of valid doses received) from the estimated up-to-date coverage (based on number of doses received regardless of age or spacing).

RESULTS

Overall, 10.5% (+/-0.6%) of children had received at least one invalid dose of vaccine. Of the invalid doses, 51% were hepatitis B, 100% of which were the third dose; 19% were diphtheria-tetanus-pertussis (DTP/DTaP), 92% of which were the fourth dose; 12% were measles-containing vaccine (MCV); 15% were varicella vaccine; and 4% were polio vaccine, 96% of which were the first dose. Excluding invalid doses resulted in a small change in vaccination coverage: 2.2% for DTP/DTaP, 0.7% for polio, 6.5% for hepatitis B, 1.4% for MCV, and 1.7% for varicella. The vaccine purchase cost to repeat at least one invalid dose ranged from approximately $10 million (public-purchased) to approximately $18 million (private-purchased).

CONCLUSIONS

Nationally about 595,000 of children aged 19 to 35 months, born between February 1997 and May 1999, received at least one invalid dose of vaccine. The cost of revaccinating these children is substantial and may have a negative impact on parents, physicians, and vaccine purchasers. Educating immunization providers regarding proper immunization timing should be conducted to reduce the administration of invalid doses of vaccines.

Impact of the Advisory Committee on Immunization Practices' 4-day grace period in a low-income community

BACKGROUND

In 2002, the Advisory Committee on Immunization Practices (ACIP) recommended vaccine doses administered < or = 4 days before the minimum age or interval be counted as valid. The study objective was to assess the impact of the 4-day grace period on the need for revaccination and associated costs in a low-income community, compared to standard practice (i.e., repeating all doses that fall outside current ACIP guidelines).

METHODS

From 1999 to 2001, semi-annual immunization assessments of 8293 randomly selected children, aged 19-35 months, were conducted at a 16-practice network serving an underserved community in New York City. Outcome measures were rates of antigen-specific invalid doses and number of children needing revaccination, with and without the 4-day grace period. Revaccination costs were based on the Vaccines for Children (VFC) price list.

RESULTS

The 4-day grace period reduced the number of children needing revaccination from 17.1% to 12.0%, a drop of 30%. The rates of invalid doses decreased from 1.9% to 1.3%, a drop of 33%. Invalid doses for hepatitis B (HepB)-2 decreased by two thirds (69.7%); for diphtheria-tetanus-acellular pertussis (DTaP)-1, Haemophilus influenzae type b (Hib)-1 and Hib-3 by half (44.9%-50.0%); for Polio-1, Polio-2, Polio-3, and measles-mumps-rubella (MMR) by one third (31.6%-33.3%); and for DTaP-2, DTaP-3, HepB-3, and varicella by nearly one quarter (20.0%-24.0%). At these rates, revaccinating 100,000 children younger than age 3 years would cost 213,588 dollars per year, compared to 152,539 dollars with the 4-day grace period, in vaccine costs alone.

CONCLUSIONS

In a low-income community, ACIP's 4-day grace period made a significant impact on the number of children requiring revaccination and on revaccination costs. However, the number of children needing revaccination remains high.

Timeliness of childhood immunizations

OBJECTIVE

To examine the timeliness of vaccine administration among infants and young children in the United States.

METHODS

We analyzed age at receipt of vaccines among 16 211 children aged 24 to 35 months in the 2000 National Immunization Survey and examined receipt at the recommended time of each dose and selected vaccination series, as well as receipt at 4 additional time frames: acceptably early, late, never by 24 months, and too early to be considered valid. We also examined the relationship between timeliness of vaccinations and characteristics of the child, mother, and immunization provider, using multivariate logistic regression.

RESULTS

Only 9% of children received all recommended vaccines at the recommended ages. The rates varied significantly by antigen, ranging from 24% for all Haemophilus influenzae type b doses to 75% for all hepatitis B doses as recommended. Overall, 55% of children did not receive all recommended doses by 24 months of age, and 8% of children received at least 1 vaccination dose too early to be considered valid. Factors associated with not receiving all vaccines as recommended were having more children in the household, mothers younger than 30 years, use of public providers, and multiple vaccination providers.

CONCLUSIONS

By 24 months of age, 9 of 10 children received at least 1 vaccine outside the recommended age ranges. High vaccination status of children at 24 months of age does not reflect the reality that many vaccinations are not given at the appropriate ages. Timeliness of vaccination is critical to prevent disease outbreaks, protect children through their first 2 years of life, and minimize the need to repeat doses.