Post-vaccine Introduction Research Articles

Genetic characterisation of Malawian pneumococci prior to the roll-out of the PCV13 vaccine using a high-throughput whole genome sequencing approach.

BackgroundMalawi commenced the introduction of the 13-valent pneumococcal conjugate vaccine (PCV13) into the routine infant immunisation schedule in November 2011. Here we have tested the utility of high throughput whole genome sequencing to provide a high-resolution view of pre-vaccine pneumococcal epidemiology and population evolutionary trends to predict potential future change in population structure post introduction.MethodsOne hundred and twenty seven (127) archived pneumococcal isolates from randomly selected adults and children presenting to the Queen Elizabeth Central Hospital, Blantyre, Malawi underwent whole genome sequencing.ResultsThe pneumococcal population was dominated by serotype 1 (20.5% of invasive isolates) prior to vaccine introduction. PCV13 is likely to protect against 62.9% of all circulating invasive pneumococci (78.3% in under-5-year-olds). Several Pneumococcal Molecular Epidemiology Network (PMEN) clones are now in circulation in Malawi which were previously undetected but the pandemic multidrug resistant PMEN1 lineage was not identified. Genome analysis identified a number of novel sequence types and serotype switching.ConclusionsHigh throughput genome sequencing is now feasible and has the capacity to simultaneously elucidate serotype, sequence type and as well as detailed genetic information. It enables population level characterization, providing a detailed picture of population structure and genome evolution relevant to disease control. Post-vaccine introduction surveillance supported by genome sequencing is essential to providing a comprehensive picture of the impact of PCV13 on pneumococcal population structure and informing future public health interventions.

The fundamental link between pneumococcal carriage and disease

Streptococcus pneumoniae (pneumococcus) is a major cause of worldwide mortality and morbidity, and to a large extent is vaccine-preventable. Nasopharyngeal carriage of pneumococcus precedes disease and is the source of pneumococcal spread between people. The use of vaccine effect on carriage as part of the vaccine licensure and post-vaccine introduction evaluation could facilitate and expand the licensure of new, life-saving pneumococcal vaccines and enable a comprehensive estimate of population effects after vaccine introduction. The authors provide a review of the evidence supporting pneumococcal carriage at the individual level as an immediate and necessary precursor to pneumococcal disease. Based on such a causal link between carriage and disease, the authors emphasize the role of information on pneumococcal carriage in vaccine trials and in public health decision-making.

Impact of rotavirus vaccination on childhood gastroenteritis-related mortality and hospital discharges in Panama

Rotavirus vaccination was introduced in Panama in March 2006. This study was carried out in order to describe the trends in gastroenteritis-related (GER) hospitalizations and mortality in children <5 years of age during the pre- and post-vaccination periods. Data from the Expanded Program on Immunization (Ministry of Health) were used to calculate vaccine coverage. GER mortality and hospitalizations were obtained through database review of the Contraloría General de la República and hospital discharge databases of five sentinel hospitals, for the period 2000-2008. Mean rates of GER mortality and mean numbers of hospitalizations during the baseline pre-vaccination period (2000-2005) were compared to those of 2007 and 2008. National coverage for the second rotavirus vaccine dose increased from 30% in 2006 to 62% in 2007 and 71% in 2008, varying from 62% in the West region to 77% in the Panama region. Overall, at 2-years post-vaccine introduction, the GER mortality rate in Panama had decreased by 50% (95% confidence interval (CI) 46-54). During 2000-2005, the GER mortality rate in children (<1 year) was 73/100 000, decreasing by 45% (95% CI 40-51) in 2008. In children aged 1-4 years, the GER mortality rate was 20.3/100 000 (2000-2005), decreasing by 54% (95% CI 48-60) in 2008. The Panama region registered the highest mortality rate reduction (69%; 95% CI 58-81) for 2008. During 2008, GER hospitalizations among children <5 years of age decreased by 30% (95% CI 21-37) from the mean number of hospitalizations during 2000-2005. A substantial reduction in GER mortality and hospitalizations was observed following the introduction of rotavirus vaccine in Panama.

Co-dominance of G1 and emerging G3 rotaviruses in Hong Kong: A three-year surveillance in three major hospitals

Background The World Health Organization recommends rotavirus vaccines be included in all national immunization programs as part of a strategy to control diarrhoeal diseases. Sentinel surveillance is advised to monitor impact post-vaccine introduction and to document changes in genotype distribution. Objectives To determine the molecular epidemiology of circulating rotaviruses in Hong Kong prior to implementation of universal rotavirus vaccination. Study design From December 2004 through December 2007, 830 rotavirus-positive stool samples from subjects admitted for acute diarrhea to three major hospitals in Hong Kong were examined. The electropherotypes, and the G and P genotypes of these rotaviruses were determined. Phylogenetic analysis of the VP7 gene was performed. Results G3P[8] was the dominant genotype (46.1%), followed by G1P[8] (36.5%) and G9P[8] (9.2%). A total of 35 electropherotypes were identified. The G3 and G1 strains had high sequence similarities among themselves and were clustered with strains from Asia particularly mainland China. The G9 strains were clustered with the globally spreading strains. G12 and G4 were not found. The prevalence of rotavirus infection peaked in winter season when temperature was low, atmospheric pressure was high, relative humidity was low and rainfall was negligible. Conclusions Genotype G3 and G1 were the dominant rotaviruses circulating in Hong Kong between 2004 and 2007. Strains were mainly related with those from mainland China. Ongoing surveillance of circulating genotypes should continue in anticipation of universal rotavirus vaccine introduction.

Evaluation of potential medical and economic benefits of universal rotavirus vaccination in Greece

To evaluate the potential benefits of introducing universal rotavirus (RV) vaccination in Greece. A decision analytic model was developed to compare the burden and cost of rotavirus gastroenteritis (RVGE) with and without a universal RV vaccination (88% vaccination coverage) for a cohort of children followed from birth until the age of five. Universal RV vaccination would substantially decrease the RVGE burden on the National Health System by reducing RVGE-related hospitalizations/emergency visits and medical consultations by 83% and 75%, respectively. Total RVGE-related costs was estimated at about 7.6 M€ and would be reduced by 5.9 M€ (-78%) if RV vaccination was introduced. A rapid effect is expected with 76% of cases and 84% of costs avoided would be averted within 2 years postvaccine introduction. The societal benefit would also be significant: total annual number of RVGE cases and parent's lost work days would be reduced by 67% and 78%, respectively. Including indirect costs, the total disease cost reduction would be 9 M€. Introduction of universal RV vaccination in Greece could offer considerable medical and economic benefits for the National Health System and society. Potential herd immunity would improve results in favour of vaccination.

Remarkable Postvaccination Spatiotemporal Changes in United States Rotavirus Activity

Analyses of US laboratory surveillance data during 1991 to 2004 established annual peak rotavirus activity occurred first in the Southwest and last in the Northeast. We compared spatiotemporal patterns during the 2 years preceding vaccine introduction in 2006 with the first 2 years following introduction. The postvaccine introduction years failed to demonstrate the typical Southwest to Northeast spread of rotavirus activity.

Sustained Decline in Rotavirus Detections in the United States Following the Introduction of Rotavirus Vaccine in 2006

Following implementation of the rotavirus vaccination program in 2006, rotavirus activity in the United States declined dramatically in 2007-2008 but increased slightly in 2008-2009, despite greater vaccine uptake. To further evaluate impact of the vaccine program, we assessed trends in rotavirus testing and detection during 2009-2010. We examined rotavirus testing data from July 2000 to June 2010 from the National Respiratory and Enteric Viruses Surveillance System to compare rotavirus season timing and peak activity in the pre- and postvaccine introduction eras. Rotavirus season onset was defined as the first of 2 consecutive weeks during which the percentage of specimens testing positive for rotavirus was ≥ 10%. To assess trends in rotavirus testing and detection, we restricted the analyses to 25 laboratories that reported for ≥ 26 weeks per season from 2000 to 2010. During 2009-2010, the threshold for the start of the rotavirus season was never achieved nationally or in the North, Midwest, or West. Activity in the South met this threshold but the season duration was substantially shorter and of lower magnitude than in all previous pre- and postvaccine introduction seasons. Nationally and within each region, the peak week was more delayed and the peak proportion of positive tests was substantially lower than all previous seasons. The total number of tests performed declined by 23%, and the number of positive tests declined by 86%. Rotavirus activity was substantially diminished during the 2009-2010 rotavirus season compared with the prevaccine baseline and the 2 previous postvaccine introduction seasons. These sustained declines over 3 rotavirus seasons reaffirm the health benefits of the US rotavirus vaccination program.

Herpes zoster in Australia: evidence of increase in incidence in adults attributable to varicella immunization?

Rates of herpes zoster (HZ) hospitalizations, antiviral prescriptions, and New South Wales emergency-department presentations for age groups <20, 20-39, 40-59 and ⩾60 years were investigated. Trends were analysed using Poisson regression to determine if rates increased following funding of varicella immunization in Australia in November 2005. The regression analysis revealed significantly increasing trends of between 2% and 6% per year in both antiviral prescriptions and emergency-department presentations in all except the <20 years age group. When considered together, the differential changes in rates observed by age group provides preliminary evidence to indicate that HZ incidence is increasing in adults aged >20 years. However, it is not possible to attribute the increasing trends in HZ observed directly to the varicella immunization programme, and continued monitoring and analyses of data for a longer duration, both pre- and post-vaccine introduction, is required.