Effectiveness of the trivalent influenza vaccine in Navarre, Spain, 2010-2011: a population-based test-negative case-control study.

BACKGROUND: Some studies have evaluated vaccine effectiveness in preventing outpatient influenza while others have analysed its effectiveness in preventing hospitalizations. This study evaluates the effectiveness of the trivalent influenza vaccine in preventing outpatient illness and hospitalizations from laboratory-confirmed influenza in the 2010-2011 season. METHODS: We conducted a nested case-control study in the population covered by the general practitioner sentinel network for influenza surveillance in Navarre, Spain. Patients with influenza-like illness in hospitals and primary health care were swabbed for influenza testing. Influenza vaccination status and other covariates were obtained from health care databases. Using logistic regression, the vaccination status of laboratory-confirmed influenza cases was compared with that of test-negative controls, adjusting for age, sex, comorbidity, outpatient visits in the previous 12 months, health care setting, time between symptom onset and swabbing, period and A(H1N1)pdm09 vaccination. Effectiveness was calculated as (1-odds ratio)x100. RESULTS: The 303 confirmed influenza cases (88% for A(H1N1)pdm09 influenza) were compared with the 286 influenza test-negative controls. The percentage of persons vaccinated against influenza was 4.3% and 15.7%, respectively (p<0.001). The adjusted estimate of effectiveness was 67% (95% CI: 24%, 86%) for all patients and 64% (95% CI: 8%, 86%) in those with an indication for vaccination (persons age 60 or older or with major chronic conditions). Having received both the 2010-2011 seasonal influenza vaccine and the 2009-2010 pandemic influenza vaccine provided 87% protection (95% CI: 30%, 98%) as compared to those not vaccinated. CONCLUSION: The 2010-2011 seasonal influenza vaccine had a moderate protective effect in preventing laboratory-confirmed influenza.

Effectiveness of the 7-valent pneumococcal conjugate vaccine: a population-based case-control study.

BACKGROUND: The 7-valent pneumococcal conjugate vaccine (PCV7) has shown high efficacy in preventing invasive pneumococcal disease (IPD) caused by vaccine serotypes. We aimed to assess the overall effectiveness of PCV7 against IPD in Navarra, Spain. METHODS: All children aged <5 years who were diagnosed with IPD during the period 2001-2005 (n=85) and 5 control subjects per case patient (n=425), individually matched by birth date and birth hospital, were analyzed. Vaccination records were obtained from the regional immunization registry. Conditional logistic regression was used to estimate odds ratios. RESULTS: Eighteen case patients (21%) and 114 control subjects (27%) had received >or=1 dose of PCV7. PCV7 serotypes were responsible for 34 (51%) of the cases in unvaccinated children. The overall effectiveness for case prevention was 31% (odds ratio, 0.69; 95% confidence interval, 0.37-1.27). In a separate analysis, vaccination with PCV7 was 88% effective in preventing IPD due to vaccine serotypes (odds ratio, 0.12; 95% confidence interval, 0.02-0.91) and was associated with a higher risk of IPD due to nonvaccine serogroups (odds ratio, 6.16; 95% confidence interval, 1.63-23.3). CONCLUSIONS: These data reveal a higher risk of IPD caused by non-PCV7 serogroups among vaccinated children. Consequently, the overall effectiveness of PCV7 for IPD prevention may be greatly reduced.

[Invasive pneumococcal disease in children younger than 5 years in Navarra, Spain (2000-2005). Impact of the conjugate vaccine]. / Enfermedad neumocócica invasiva en la población menor de 5 años de edad de Navarra (2000-2005): impacto de la vacuna conjugada.

BACKGROUND AND OBJECTIVE: The 7-valent pneumococcal conjugate vaccine (PCV7) has been commercialized in Spain since June 2001. We aim to evaluate the impact of this vaccine in the incidence of invasive pneumococcal disease (IPD) in Navarre. POPULATION AND METHOD: The laboratories of microbiology of Navarre declare all the isolations of Streptococcus pneumoniae in samples of normally sterile corporal fluids. We analyzed the incidence of IPD in children younger than 5 years between weeks 41 of 2000 and 40 of 2005. RESULTS: The doses of PCV7 sold up to 2005 would provide a cover of 27% in children younger than 5 years, having assumed 4 dose schedules. In the 5 seasons, 103 cases of IPD were diagnosed. From the 2 first seasons (2000-2002) to the last one (2004-2005) a reduction of 69% in the incidence rate of IPD caused by vaccine serotypes was observed (from 33 to 10 cases by 100,000 children under 5 years; p = 0.003). Between those same periods the incidence of IPD caused by non-vaccine serotypes increased a 36% (from 42 to 57 by 100,000; p = 0.405). The global incidence of IPD diminished a 12% (from 77 to 67 by 100,000; p = 0.689). The percentage of cases that had received PCV7 increased until 45% in season 2004-2005 (p < 0.001). The meningitis and bacteraemic pneumonias supposed 42% of the IPD, without significant changes during the period (p = 0.442). CONCLUSIONS: Since the PCV7 was marketed the pattern of serotypes has changed, but the expected reduction in the total IPD incidence has not been achieved.

Household transmission of influenza A(H1N1)pdm09 in the pandemic and post-pandemic seasons.

BACKGROUND: The transmission of influenza viruses occurs person to person and is facilitated by contacts within enclosed environments such as households. The aim of this study was to evaluate secondary attack rates and factors associated with household transmission of laboratory-confirmed influenza A(H1N1)pdm09 in the pandemic and post-pandemic seasons. METHODS: During the 2009-2010 and 2010-2011 influenza seasons, 76 sentinel physicians in Navarra, Spain, took nasopharyngeal and pharyngeal swabs from patients diagnosed with influenza-like illness. A trained nurse telephoned households of those patients who were laboratory-confirmed for influenza A(H1N1)pdm09 to ask about the symptoms, risk factors and vaccination status of each household member. RESULTS: In the 405 households with a patient laboratory-confirmed for influenza A(H1N1)pdm09, 977 susceptible contacts were identified; 16% of them (95% CI 14-19%) presented influenza-like illness and were considered as secondary cases. The secondary attack rate was 14% in 2009-2010 and 19% in the 2010-2011 season (p=0.049), an increase that mainly affected persons with major chronic conditions. In the multivariate logistic regression analysis, the risk of being a secondary case was higher in the 2010-2011 season than in the 2009-2010 season (adjusted odds ratio: 1.72; 95% CI 1.17-2.54), and in children under 5 years, with a decreasing risk in older contacts. Influenza vaccination was associated with lesser incidence of influenza-like illness near to statistical significance (adjusted odds ratio: 0.29; 95% CI 0.08-1.03). CONCLUSION: The secondary attack rate in households was higher in the second season than in the first pandemic season. Children had a greater risk of infection. Preventive measures should be maintained in the second pandemic season, especially in high-risk persons.

[Impact of vaccination against influenza (H1N1) 2009 in Navarre: comparison of different scenarios]. / Impacto de la vacunación frente a la gripe (H1N1) 2009 en Navarra: comparación de diferentes escenarios.

BACKGROUND: A specific vaccination campaign against influenza A (H1N1) was conducted in 2009. We evaluated its impact in Navarre. METHODS: In the cohort of non-institutionalised population with chronic diseases covered by the Navarre Health Service (n=131,333), assuming 100% effectiveness from day 8 after administration of the pandemic vaccine, we estimated its impact on the prevention of influenza A (H1N1) 2009 cases and hospitalisations between weeks 47/2009 and 3/2010. RESULTS: In the nine weeks of the study, 973 cases of influenza syndrome were diagnosed (7 per 1000); but only 28% were due to influenza A (H1N1) 2009. In addition, there were 14 hospitalisations with virological confirmation (11 per 100,000). With 19% coverage with the pandemic vaccine (versus 40% with the seasonal vaccine), 7.7% of cases and 10.5% of hospitalisations were prevented during the study period. For each case prevented, 1092 doses of pandemic vaccine were administered, and for each hospitalisation avoided 15,021 doses were administered. If coverage had been the same as for the seasonal vaccine, it would have been possible to prevent 16.2% of cases and 22.2% of hospitalisations. If coverage had been double than for the seasonal vaccine and vaccination campaign had taken place two weeks earlier, it would have been possible to prevent 70.7% of cases and 68.0% of hospitalizations, with 261 doses needed to prevent one case and 6206 doses to avoid one hospitalisation. CONCLUSION: Despite the high effectiveness of the vaccine, its impact in Navarre has been minimal due to low coverage and late initiation of the vaccination campaign.

Effectiveness of the monovalent influenza A(H1N1)2009 vaccine in Navarre, Spain, 2009-2010: cohort and case-control study.

We defined a population-based cohort (596,755 subjects) in Navarre, Spain, using electronic records from physicians, to evaluate the effectiveness of the monovalent A(H1N1)2009 vaccine in preventing influenza in the 2009-2010 pandemic season. During the 9-week period of vaccine availability and circulation of the A(H1N1)2009 virus, 4608 cases of medically attended influenza-like illness (MA-ILI) were registered (46 per 1000 person-years). After adjustment for sociodemographic covariables, outpatient visits and major chronic conditions, vaccination was associated with a 32% (95% CI: 8-50%) reduction in the overall incidence of MA-ILI. In a test negative case-control analysis nested in the cohort, swabs from 633 patients were included, and 123 were confirmed for A(H1N1)2009 influenza. No confirmed case had received A(H1N1)2009 vaccine versus 9.6% of controls (p<0.001). The vaccine effectiveness in preventing laboratory-confirmed influenza was 89% (95% CI: 36-100%) after adjusting for age, health care setting, major chronic conditions and period. Pandemic vaccine was effective in preventing MA-ILI and confirmed cases of influenza A(H1N1)2009 in the 2009-2010 season.

Effectiveness of Jeryl Lynn-containing vaccine in Spanish children.

We evaluated the effectiveness of the Jeryl Lynn strain vaccine in a large outbreak of mumps in Navarre, Spain, 2006-2008. Each of the 241 cases of mumps occurring in children over 15 months of age born between 1998 and 2005 was compared with 5 controls individually matched by sex, birth date, district of residence and paediatrician. Vaccination history was obtained blindly from clinical records. Conditional logistic regression was used to obtain the matched odds ratios (ORs), and effectiveness was calculated as 1-OR. Some 70% of cases had received one dose of measles-mumps-rubella vaccine, and 24% had received two doses. Overall vaccine effectiveness was 72% (95% CI, 39-87%). Two doses were more effective (83%; 54-94%) than a single dose (66%; 25-85%). Among vaccinated children, risk was higher in those who had received the first dose after 36 months of age (OR=3.1; 1.2-8.4) and those who had received the second dose 3 or more years before study enrolment (OR=10.2; 1.5-70.7). Early waning of immunity in children after the second dose may contribute to reduced vaccine effectiveness for mumps prevention.