All-Cause Pneumonia Hospitalizations in Children <2 Years Old in Sweden, 1998 to 2012: Impact of Pneumococcal Conjugate Vaccine Introduction

Abstract

BackgroundIn late 2007, some Swedish County Councils started 7-valent pneumococcal conjugate vaccine (PCV7) implementation for children, and PCV7 was included in the national immunization program in 2009. By 2010, both PCV10 and PCV13 were licensed, and the selection of vaccine was subject to County Councils tenders. This study investigated the impact of the order of PCV introduction into vaccination programs on the incidence of all-cause pneumonia hospitalizations in children <2 years-old.MethodsUsing population-based data from the publicly available National Inpatient Registry, the incidence of inpatient pneumonia (ICD-10 J12-J18) hospitalizations by County Councils among children <2 years old was identified between 1998 and 2012. Incidence rate ratios (IRR; 95% CI) were calculated during the nationwide implementation of PCV7 and then between County Councils, as based on the higher-valent vaccine chosen for a program.ResultsThere was a lower risk of all-cause pneumonia hospitalization among <2 year-old children following the introduction of PCV7, as compared to the pre-PCV7 period (0.77; 0.63–0.93). A decreased risk of all-cause pneumonia was also observed in the County Councils that followed the order PCV7 then PCV13 (0.82; 0.66–1.01), while no trend was observed in County Councils with a program in the order PCV7 then PCV10 (1.03; 0.82–1.30). When comparing the higher-valent vaccines, there was a 21% (0.79; 0.66–0.96) lower risk for childhood pneumonia hospitalization in County Councils finally using PCV13 as compared to the experience in County Councils that ultimately adopted PCV10.ConclusionsAmong children <2 years-old, all-cause pneumonia hospitalizations were significantly reduced by 23% one to two years after introduction of PCV7 vaccination in Sweden. In those County Councils that next introduced PCV13, a further decline in all-cause pneumonia hospitalization was observed, in contrast to those County Councils that followed with PCV10; this 21% lower risk for childhood pneumonia hospitalization was statistically significant.

Effect of co-trimoxazole on mortality in HIV-exposed but uninfected children in Botswana (the Mpepu Study): a double-blind, randomised, placebo-controlled trial

“…This lower HEU mortality rate may have been achieved through improvements in clinical care and in vaccination coverage over time; improved maternal health through widespread ART availability; or safer feeding and formula preparation practices. Of importance, the Prevnar and rotavirus vaccines were introduced in Botswana during the study period (in mid-2012), and these may have reduced mortality from respiratory and diarrheal diseases 35–38 . It is also possible that mortality was lower than anticipated because infants deemed unlikely to survive to 18 months (or dying before 34 days) were not randomized.…”

Response to Wu et al. — Cost-effectiveness analysis of infant pneumococcal vaccination in Malaysia and Hong Kong

“…Comparing data across different post-marketing surveillance studies is difficult due to the large number of confounders not accounted for in the study designs and any inferences thus made are inherently biased. This can be observed from a recent study in Sweden by Berglund et al 27 . That study looked at different county councils in Sweden that used PCV7 before switching to either PCV13 or PHiD-CV.…”

“…That study looked at different county councils in Sweden that used PCV7 before switching to either PCV13 or PHiD-CV. The authors conclude that the difference in the rates of hospitalization from all-cause pneumonia between the 2 groups can be attributed to the difference in the valence of the vaccines used 27 . However, a closer look at the data shows that even in the period where the 2 groups of county councils used PCV7, the rates of all-cause pneumonia hospitalization are markedly different despite the demographic and socio-economic status similarities; implying the presence of a confounding factor 27 .…”

“…Other flaws in the study design, such as the lack of consideration of a significant transition period between vaccines, also complicate the ability to make any inference between the 2 groups. The authors report a reduction of 37% (incidence rate ratio [IRR] 0.63; 95% CI: 0.54, 0.74) in the risk of hospitalization in counties that used PCV7 followed by PCV13 compared to the pre-PCV period 27 . However, another study performed in Stockholm, Sweden during the same period by Lindstrand et al.…”

“…The authors conclude that the difference in the rates of hospitalization from all-cause pneumonia between the 2 groups can be attributed to the difference in the valence of the vaccines used 27 . However, a closer look at the data shows that even in the period where the 2 groups of county councils used PCV7, the rates of all-cause pneumonia hospitalization are markedly different despite the demographic and socio-economic status similarities; implying the presence of a confounding factor 27 . Other flaws in the study design, such as the lack of consideration of a significant transition period between vaccines, also complicate the ability to make any inference between the 2 groups.…”