Itziar Casado

Effect of influenza vaccination on the prognosis of hospitalized influenza patients

ABSTRACT Objectives: This study aimed to assess whether influenza vaccination reduces the risk of severe and fatal outcomes in influenza inpatients aged ≥65 years. Methods: During the 2013–2014 influenza season persons aged ≥65 years hospitalized with laboratory-confirmed influenza were selected in 19 Spanish hospitals. A severe influenza case was defined as admission to the intensive care unit, death in hospital or within 30 days after admission. Logistic regression was used to compare the influenza vaccination status between severe and non-severe influenza inpatients. Results: Of 433 influenza confirmed patients, 81 (19%) were severe cases. Vaccination reduced the risk of severe illness (odds ratio: 0.57; 95%CI: 0.33–0.98). The cumulative number of influenza vaccine doses received since the 2010–2011 season was associated with a lower risk of severe influenza (odds ratio: 0.78; 95% CI 0.66–0.91). Conclusion: Adherence to seasonal influenza vaccination in the elderly may reduce the risk of severe influenza outcomes.

Effectiveness of subunit influenza vaccination in the 2014-2015 season and residual effect of split vaccination in previous seasons.

BACKGROUND In Navarra, Spain, subunit vaccine was first used in the 2014-2015 season, whereas trivalent split-virion influenza vaccines had been used in previous seasons. We estimate the effectiveness of the subunit vaccine in the current season and split vaccine in the two previous seasons against laboratory-confirmed influenza in the 2014-2015 season. METHODS Patients with influenza-like illness hospitalized or attended by sentinel general practitioners were swabbed for influenza testing. The previous and current vaccine status of laboratory-confirmed cases was compared to test-negative controls. RESULTS Among 1213 patients tested, 619 (51%) were confirmed for influenza virus: 52% influenza A(H3N2), 46% influenza B, and 2% A(H1N1)pdm09. The overall effectiveness for subunit vaccination in the current season was 19% (95% confidence interval [CI]: -13 to 42), 2% (95%CI: -47 to 35) against influenza A(H3N2) and 32% (95%CI: -4 to 56) against influenza B. The effectiveness against any influenza was 67% (95%CI: 17-87) for 2012-2013 and 2013-2014 vaccination only, 42% (95%CI: -31 to 74) for 2014-2015 vaccination only, and 38% (95%CI: 8-58) for vaccination in the 2012-2013, 2013-2014 and 2014-2015 seasons. The same estimates against influenza A(H3N2) were 47% (95%CI: -60 to 82), -54% (95%CI: -274 to 37) and 28% (95%CI: -17 to 56), and against influenza B were 82% (95%CI: 19-96), 93% (95%CI: 45-99) and 43% (95%CI: 5-66), respectively. CONCLUSION These results suggest a considerable residual protection of split vaccination in previous seasons, low overall effectiveness of current season subunit vaccination, and possible interference between current subunit and previous split vaccines.

Effect of Repeated Vaccination With the Same Vaccine Component Against 2009 Pandemic Influenza A(H1N1) Virus

Background The 2009 pandemic influenza A(H1N1) (A[H1N1]pdm09) vaccine component has remained unchanged from 2009. We estimate the effectiveness of current and prior inactivated influenza A(H1N1)pdm09 vaccination from influenza seasons 2010-2011 to 2015-2016. Methods Patients attended with influenza-like illness were tested for influenza. Four periods with continued A(H1N1)pdm09 circulation were included in a test-negative design. Results We enrolled 1278 cases and 2343 controls. As compared to individuals never vaccinated against influenza A(H1N1)pdm09, the highest effectiveness (66%; 95% confidence interval, 49%-78%) was observed in those vaccinated in the current season who had received 1-2 prior doses. The effectiveness was not statistically lower in individuals vaccinated in the current season only (52%) or in those without current vaccination and >2 prior doses (47%). However, the protection was lower in individuals vaccinated in the current season after >2 prior doses (38%; P = .009) or those currently unvaccinated with 1-2 prior doses (10%; P < .001). Current-season vaccination improved the effect in individuals with 1-2 prior doses and did not modify significantly the risk of influenza in individuals with >2 prior doses. Conclusion Current vaccination or several prior doses were needed for high protection. Despite the decreasing effect of repeated vaccination, current-season vaccination was not inferior to no current-season vaccination.

Combined effectiveness of prior and current season influenza vaccination in northern Spain: 2016/17 mid-season analysis

The 2016/17 mid-season vaccine effectiveness estimate against influenza A(H3N2) was 15% (95% confidence interval: −11 to 35) in Navarre. Comparing to individuals unvaccinated in the current and four prior seasons, effectiveness was 24% for current and 3–4 prior doses, 61% for current and 1–2 prior doses, 42% for only current vaccination, and 58% for 3–4 prior doses. This suggests moderate effectiveness for different combinations of vaccination in the current and prior seasons.

Effects of previous episodes of influenza and vaccination in preventing laboratory-confirmed influenza in Navarre, Spain, 2013/14 season

We estimated whether previous episodes of influenza and trivalent influenza vaccination prevented laboratory-confirmed influenza in Navarre, Spain, in season 2013/14. Patients with medically-attended influenza-like illness (MA-ILI) in hospitals (n = 645) and primary healthcare (n = 525) were included. We compared 589 influenza cases and 581 negative controls. MA-ILI related to a specific virus subtype in the previous five seasons was defined as a laboratory-confirmed influenza infection with the same virus subtype or MA-ILI during weeks when more than 25% of swabs were positive for this subtype. Persons with previous MA-ILI had 30% (95% confidence interval (CI): -7 to 54) lower risk of MA-ILI, and those with previous MA-ILI related to A(H1N1)pdm09 or A(H3N2) virus, had a, respectively, 63% (95% CI: 16-84) and 65% (95% CI: 13-86) lower risk of new laboratory-confirmed influenza by the same subtype. Overall adjusted vaccine effectiveness in preventing laboratory-confirmed influenza was 31% (95% CI: 5-50): 45% (95% CI: 12-65) for A(H1N1)pdm09 and 20% (95% CI: -16 to 44) for A(H3N2). While a previous influenza episode induced high protection only against the same virus subtype, influenza vaccination provided low to moderate protection against all circulating subtypes. Influenza vaccine remains the main preventive option for high-risk populations.

Influenza vaccine effectiveness in preventing inpatient and outpatient cases in a season dominated by vaccine-matched influenza B virus

Studies that have evaluated the influenza vaccine effectiveness (VE) to prevent laboratory-confirmed influenza B cases are uncommon, and few have analyzed the effect in preventing hospitalized cases. We have evaluated the influenza VE in preventing outpatient and hospitalized cases with laboratory-confirmed influenza in the 2012–2013 season, which was dominated by a vaccine-matched influenza B virus. In the population covered by the Navarra Health Service, all hospitalized patients with influenza-like illness (ILI) and all ILI patients attended by a sentinel network of general practitioners were swabbed for influenza testing, and all were included in a test-negative case-control analysis. VE was calculated as (1-odds ratio)×100. Among 744 patients tested, 382 (51%) were positive for influenza virus: 70% for influenza B, 24% for A(H1N1)pdm09, and 5% for A(H3N2). The overall estimate of VE in preventing laboratory-confirmed influenza was 63% (95% confidence interval (CI): 34 to 79), 55% (1 to 80) in outpatients and 74% (33 to 90) in hospitalized patients. The VE was 70% (41 to 85) against influenza B and 43% (−45 to 78) against influenza A. The VE against virus B was 87% (52 to 96) in hospitalized patients and 56% in outpatients (−5 to 81). Adjusted comparison of vaccination status between inpatient and outpatient cases with influenza B did not show statistically significant differences (odds ratio: 1.13; p = 0.878). These results suggest a high protective effect of the vaccine in the 2012–2013 season, with no differences found for the effect between outpatient and hospitalized cases.

Interim effectiveness of trivalent influenza vaccine in a season dominated by lineage mismatched influenza B, northern Spain, 2017/18

The 2017/18 interim estimate of trivalent influenza vaccine effectiveness (VE) was 39% (95% confidence interval: 20–54) in Navarre. Compared with individuals unvaccinated in the current and five previous seasons, VE against influenza B was 41% for current and any prior doses, 67% for current vaccination only, and 22% for any prior doses, and 43%, 51% and 54%, respectively against influenza A(H3N2). This suggests moderate VE despite predominance of lineage mismatched influenza B.

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.

Exhaustividad de la estadística de mortalidad de Navarra

Fundamentos: La esperanza de vida al nacer de las mujeres de Navarra se encuentra entre las mas altas de Europa. El objetivo del estudio es evaluar la exhaustividad de la estadistica oficial de mortalidad de Navarra en 2009 y su impacto en la estimacion de la esperanza de vida. Metodos: Se compara el numero oficial de muertes del Instituto Nacional de Estadistica (INE) con el obtenido mediante busqueda en multiples fuentes: historia clinica informatizada de atencion especializada, Instituto Navarro de Medicina Legal e INE incluyendo defunciones recibidas con retraso. Resultados: Se contabilizaron 5.249 fallecimientos, de los cuales 103 no estaban incluidos en los datos oficiales del INE. Teniendo en cuenta unicamente las defunciones ocurridas en territorio espanol, que es a lo que hace referencia la estadistica oficial de mortalidad, la exhaustividad fue del 98,4%. La esperanza de vida al nacer en el ano 2009 descendio de de 86,6 a 86,4 anos en las mujeres y de 80,0 a 79,6 anos en los hombres tras corregir el subregistro. Conclusiones: Se descarta la existencia de un subregistro significativo en la estadistica oficial de mortalidad y se confirma la elevada longevidad de las mujeres de Navarra que, con una esperanza de vida al nacer de 86,4 anos, ocupan la primera posicion en Europa.

Repeated influenza vaccination for preventing severe and fatal influenza infection in older adults: a multicentre case–control study

BACKGROUND: The effectiveness of repeated vaccination for influenza to prevent severe cases remains unclear. We evaluated the effectiveness of influenza vaccination on preventing admissions to hospital for influenza and reducing disease severity. METHODS: We conducted a case–control study in 20 hospitals in Spain during the 2013/14 and 2014/15 influenza seasons. Community-dwelling adults aged 65 years or older who were admitted to hospital for laboratory-confirmed influenza were matched with inpatient controls by sex, age, hospital and admission date. The effectiveness of vaccination in the current and 3 previous seasons in preventing influenza was estimated for inpatients with nonsevere influenza and for those with severe influenza who were admitted to intensive care units (ICUs) or who died. RESULTS: We enrolled 130 inpatients with severe and 598 with nonsevere influenza who were matched to 333 and 1493 controls, respectively. Compared with patients who were unvaccinated in the current and 3 previous seasons, adjusted effectiveness of influenza vaccination in the current and any previous season was 31% (95% confidence interval [CI] 13%–46%) in preventing admission to hospital for nonsevere influenza, 74% (95% CI 42%–88%) in preventing admissions to ICU and 70% (95% CI 34%–87%) in preventing death. Vaccination in the current season only had no significant effect on cases of severe influenza. Among inpatients with influenza, vaccination in the current and any previous season reduced the risk of severe outcomes (adjusted odds ratio 0.45, 95% CI 0.26–0.76). INTERPRETATION: Among older adults, repeated vaccination for influenza was twice as effective in preventing severe influenza compared with nonsevere influenza in patients who were admitted to hospital, which is attributable to the combination of the number of admissions to hospital for influenza that were prevented and reduced disease severity. These results reinforce recommendations for annual vaccination for influenza in older adults.