Effectiveness of Haemophilus influenzae Type b Conjugate Vaccine on Radiologically-Confirmed Pneumonia in Young Children in Pakistan

Abstract

Objective The effectiveness of Haemophilus influenzae type b (Hib) vaccine in preventing severe pneumonia in Asian children has been questioned, and many large Asian countries yet to introduce Hib conjugate vaccine in immunization programs. The primary objective of this study was to assess Hib conjugate vaccine effectiveness (VE) on radiologically-confirmed pneumonia in children born after introduction of Hib conjugate vaccine in Pakistan. Study design A matched case-control study enrolled cases of radiologically-confirmed pneumonia in several hospitals serving low-income populations during 2009–2011. Cases were matched by age and season with 3 hospital and 5 neighborhood controls. Pneumonia was diagnosed using standardized World Health Organization criteria for chest radiograph interpretation. Matched OR were estimated for VE. Results A total of 1027 children with radiologically-confirmed pneumonia were enrolled; 975 cases, 2925 hospital controls, and 4875 neighborhood controls were analyzed. The coverage for 3 doses of diphtheria-tetanus-pertussis-hepatitis B-Hib conjugate vaccine was 13.7%, 18%, and 22.7% in cases, hospital controls and neighborhood controls, respectively. Estimated Hib VE for radiologically-confirmed pneumonia was 62% with 3 doses of vaccine using hospital controls and 70% using neighborhood controls. Conclusions Hib conjugate vaccine prevented a significant fraction of radiologically-confirmed pneumonia in children in Pakistan. Maximizing impact on child survival needs improved immunization coverage.

Respiratory risks from household air pollution in low and middle income countries

“…The longevity of population level benefits might be shortened by serotype replacement occurring rapidly after vaccine introduction (as seen with seven-valent pneumococcal conjugate vaccines),130–132 and by subsequent increases in non-vaccine-serotype pneumonia. H influenzae type b vaccines reduce pneumonia burden in low-income countries,133 and some evidence also supports a herd effect 134. However, vaccination will not affect the burden of colonisation with non-typable (not type b) H influenzae , which is substantially more common in developing countries than is H influenzae type b135 and has long been recognised as an important cause of pneumonia 127,136.…”

Progress towards Demonstrating the Impact of Haemophilus influenzae Type b Conjugate Vaccines Globally

“…15 The report from the surveillance network established in the WHO Eastern Mediterranean region 16 specifically addresses the benefits of conducting such surveillance using standardized protocols, but also the practical and field challenges of coordinating a surveillance network, especially as many regions face political instability and have difficulties transferring specimens and supplies across borders. It remains difficult to explain the high estimates of vaccine effectiveness reported through case-control studies, as seen in this supplement in Ukraine 17 and Pakistan, 18 and as was observed earlier in Bangladesh. 19 Various reasons related to study design and control selection have been proposed and efforts are currently ongoing to systematically avoid such biases in future studies.…”

Early indication for a reduced burden of radiologically confirmed pneumonia in children following the introduction of routine vaccination against Haemophilus influenzae type b in Nha Trang, Vietnam

“…To date most studies that were conducted in Asia reported effectiveness estimates from case-control designs rather than population based incidence impact. Vaccine effectiveness was estimated to be 31% (−9% to 57%) in Brazil, 55% (7-78%) in children receiving three vaccine doses in Colombia, 21% (5-35%) in Gambia, 22% (−7% to 43%) in Chile, 45% (18-63%) in Ukraine and 62% (47-73%) in Pakistan [14,[29][30][31][32]. All but Gambia and Chile were case control studies.…”

“…As a result, Asian countries have been slow to include Hib vaccination into their routine schedules, and China and Thailand have still not introduced the vaccine [12]. An increasing body of evidence has been emerging that Hib substantially contributes to the burden of disease in Asia [13][14][15][16][17] and that the incidence and mortality associated with Hib in Southeast Asia are in fact similar to levels observed in many other parts of the world, in particular in the Americas [1]. This includes recent findings from Vietnam [18,19].…”

“…Case control studies in various settings, including Pakistan and Bangladesh reported the Hib vaccine effectiveness against all cause radiologically confirmed pneumonia (RCP) in children to be between 20 and 60% [14,[29][30][31][32][33], although methodological problems may have led to inflated effectiveness estimates. A randomised controlled trial amongst Indonesian children could not detect any protective effect against this endpoint [17], despite reporting a substantial impact on meningitis.…”