Timeliness of immunisation with the pentavalent vaccine at different levels of the health care system in the Lao People's Democratic Republic: A cross-sectional study

PLoS One. 2020 Dec 8;15(12):e0242502. doi: 10.1371/journal.pone.0242502. eCollection 2020.


Background: The timely administration of vaccines is considered to be important for both individual and herd immunity. In this study, we investigated the timeliness of the diphtheria-tetanus-whole cell pertussis-hepatitis B-Haemophilus influenzae type b (pentavalent) vaccine, scheduled at 6, 10 and 14 weeks of age in the Lao People's Democratic Republic. We also investigated factors associated with delayed immunization.

Methods: 1162 children aged 8-28 months who had received the full course of the pentavalent vaccine at different levels of the health care system were enrolled. Vaccination dates documented in hospital records and/or immunisation cards were recorded. Age at vaccination and time intervals between doses were calculated. Predictors for timely completion with the pentavalent vaccine at 24 weeks were assessed by bivariate and multivariable analyses.

Results: Several discrepancies in dates between vaccination documents were observed. In general, vaccination with the pentavalent vaccine was found to be delayed, especially in health care settings below the provincial hospital level. Compared to the central hospital level, less participants who were vaccinated at the district/health center level received the third dose by 16 (48% at the central hospital level vs. 7.1% at the district and 12.4% at the health center level) and 24 weeks of age (94.4% at the central hospital level vs 64.6% at the district-outreach and 57.4% at the health center level) respectively. In logistic regression analyses, lower education level of the mother as well as vaccination by outreach service, were independently associated with delayed completion of vaccination.

Conclusion: We observed a general delay of vaccination, especially at lower ranked facilities, which correlated with indicators of poor access to health services. This highlights the need for further improving health equity in rural areas. Age-appropriate vaccination should become a quality indicator for the national immunization programme. In addition, we recommend further training of the health care staff regarding the importance of reliable documentation of dates.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Child, Preschool
  • Diphtheria / epidemiology
  • Diphtheria / prevention & control
  • Diphtheria-Tetanus-Pertussis Vaccine / administration & dosage*
  • Educational Status
  • Female
  • Haemophilus Infections / epidemiology
  • Haemophilus Infections / prevention & control
  • Haemophilus Vaccines / administration & dosage*
  • Hepatitis B / epidemiology
  • Hepatitis B / prevention & control
  • Hepatitis B Vaccines / administration & dosage*
  • Hospitals
  • Humans
  • Immunization / statistics & numerical data*
  • Immunization Programs / organization & administration*
  • Immunization Schedule
  • Infant
  • Laos / epidemiology
  • Logistic Models
  • Male
  • Rural Population
  • Tetanus / epidemiology
  • Tetanus / prevention & control
  • Urban Population
  • Vaccines, Combined / administration & dosage*
  • Whooping Cough / epidemiology
  • Whooping Cough / prevention & control


  • Diphtheria-Tetanus-Pertussis Vaccine
  • Haemophilus Vaccines
  • Hepatitis B Vaccines
  • Vaccines, Combined

Grants and funding

This work was supported by the Ministry of Foreign and European Affairs, Luxembourg (project “Luxembourg-Laos Partnership for Research and Capacity Building in Infectious Disease Surveillance II”) and the Luxembourg Institute of Health and the AUF (l’Agence universitaire de la Francophonie). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.