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Effectiveness of Maternal Influenza Immunization in Mothers and Infants Zaman K et al N Engl J Med 2008;359:1555-64.

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Presentation on theme: "Effectiveness of Maternal Influenza Immunization in Mothers and Infants Zaman K et al N Engl J Med 2008;359:1555-64."— Presentation transcript:

1 Effectiveness of Maternal Influenza Immunization in Mothers and Infants Zaman K et al N Engl J Med 2008;359:

2 Learning Objective Epidemiology of Influenza

3 Introduction Influenza infection – Young infants and pregnant women are at increased risk for hospitalization and mortality – Maternal infection has increased risk of fetal malformation, and other illnesses – predisposes young infants to bacterial pneumonia or otitis media etc Natural maternal influenza antibodies protect infants during the first few months of life Inactivated influenza vaccine is recommended for pregnant women but is not licensed for infants younger than 6 months of age

4 Objective: To estimates the clinical effectiveness of maternal immunization with inactivated influenza vaccine on influenza illness in infants and mothers

5 Methodology Study design: Randomized controlled trial Study setting: Bangladesh (Mother’s Gift project for RCT on pneumococcal vaccines) Study subjects: 340 mothers Exclusion criteria- – Mothers with a history of systemic disease, previous complicated pregnancy or preterm delivery, spontaneous or medical abortion, congenital anomaly, and hypersensitivity to or receipt of a study vaccine in the previous 3 years Randomization: Stratified block randomization (stratified according to clinic) Concealed allocation: using sequentially numbered opaque envelopes Blinding: Double- blinding

6 Methodology Intervention: – Influenza vaccine group received inactivated influenza vaccine – Control group received 23- valent pneumococcal polysacharide vaccine Outcome: – Primary outcome – occurrence of first episode of laboratory- confirmed influenza before 24 weeks of age in infants – Other outcomes- (for both infants and mothers) Numbers of episodes of respiratory illness with fever Documented fever > 38°C Clinic visits with respiratory illness Episodes of diarrhea (non-respiratory end point for both groups) Written informed consent and ethical approval Analysis: Incidence of illness, incidence rate ratios, and vaccine effectiveness

7 Mothers screened (823) Mothers Randomized (340) Intervention Arm Control Arm Received inactivated influenza vaccine Received pneumococcal polysaccharide vaccine

8 Table1. Characteristics of patients CharacteristicsControl (N=168)Influenza vaccine (N=172) P - value Maternal age24.9 ( )25.1 ( )0.63 Maternal education10.9 (0-16)11.3 (0-16)0.42 Gravidity2 (1-7)2 (1-6)0.93 Parity1.2 (0-4)1.1 (0-4)0.80 Rooms in house4 (1-10) 0.97 Smokers in family (%) Maternal height (cm)153 ( )153 ( )0.64 Interval between vaccination and births (days) 56 (13-94)54 (0-89)

9 Table1. Characteristics of patients cont.. CharacteristicsControl (N=168)Influenza vaccine (N=172) P - value Gestational age at birth (wk) 39.3 ( )39.4 ( )0.55 Gestational age <37 wk (%) Delivery in hospital or clinic (%) Cesarean delivery (%) Birth weight (kg)3( )3.1 ( )0.08 Mean Apgar score at 1 & 5 min 7.5 and and and 0.77 Sex of infant female (%) Duration of exclusive BF (wk) 15 (1-25)14 (1-25)0.18

10 Table2. Clinical effectiveness of influenza vaccine in infants and mothers EpisodesClinical effectiveness (95% CI) Risk difference (95% CI) VariableControl (N=168)Influenza vaccine (N=172) Infants Person–months Respiratory illness with fever Any fever (6.9 to (-48.2 to -8.0) Temp > 38°C (-4.6 to 50.6)-13.7 (-28.0 to 0.5) Diarrheal disease (-30.0 to 26.0)-1.6 (-22.1 to 18.9) Clinic visit (18.2 to 58.8)-24.4 (-38.0 to -10.8) Influenza test ordered (25.4 to 64.7)-24.4 (-38.0 to -10.8) Influenza test positive (5.0 to 85.4)-6.4 (-12.2 to -0.5)

11 Table2. Clinical effectiveness of influenza vaccine in infants and mothers EpisodesClinical effectiveness (95% CI) Risk difference (95% CI) VariableControl (N=168)Influenza vaccine (N=172) Infants Person–months Respiratory illness with fever Any fever (3.7 to 57.2)-14.2 (-25.5 to -2.9) Temp > 38°C (-9.0 to 70.3)-7.3 (-14.5 to -0.1) Diarrheal disease (-24.6 to 47.8) -5.9 (-16.4 to 4.5) Clinic visit (-43.9 to 60.8) -3.2 (-9.8 to 3.4)

12 Discussion Vaccination is the single best way to protect against the flu among pregnant woman other than hand washing, staying away from ill people, and other steps can help to protect. (CDC Sept 2009) In contrast, a longitudinal, prospective study demonstrated no association between immunization with InfA/NJ and maternal, perinatal, or infant complications.(2) Efficacy- ranges from 35-93% – A study estimated protective efficacy of CAIV-T was 85% and of TIV was 71%. (3) – LAIV was 73 to 93 percent efficacious, and protection lasted more than 12 months.(6) – Efficacy against antigenically well-matched epidemic influenza strains was high at 92%.(7) – In young children, protective efficacy against culture confirmed influenza was demonstrated in a field trial with overall protective efficacy of 92% during a two year study. Vaccine was also highly protective against a strain not contained in the vaccine, with 86% protective efficacy demonstrated against this significantly drifted virus.(8) – LAIV recipients experienced 35–53% fewer cases of culture-confirmed influenza illness caused by antigenically matched strains Safety – Safe during second or third trimester of pregnancy.(1)(Flushot of TIV) – CAIV-T is safe in healthy children and should complement the use of inactivated influenza vaccine, trivalent (IIV-T) in children with underlying chronic conditions(4) – LAIV administration in children aged years with history of intermittent wheezing was safe, and was not associated with increased risk for medically-attended acute respiratory illnesses, including acute asthma exacerbation. (5, 9)

13 Conclusion Inactivated influenza vaccine reduced proven influenza illness by 63% in infants up to 6 months of age and averted approximately a third of all febrile respiratory illnesses in mothers and young infants

14 Related studies 1.Pool V, Iskander J. Safety of influenza vaccination during pregnancy. Am J Obstet Gynecol Apr;192(4): Deinard AS, Ogburn P Jr. A/NJ/8/76 influenza vaccination program: effects on maternal health and pregnancy Outcome. Am J Obstet Gynecol Jun 1;140(3): Treanor et al. Evaluation of trivalent, live, cold-adapted (CAIV-T) and inactivated (TIV) influenza vaccines in prevention of virus infection and illness following challenge of adults with wild-type influenza A (H1N1), A (H3N2), and B viruses.Vaccine Dec 10;18(9- 10): Piedra PA. Safety of the trivalent, cold-adapted influenza vaccine (CAIV-T) in children. Semin Pediatr Infect Dis Apr;13(2): Gaglani MJ. Safety of the intranasal, trivalent, live attenuated influenza vaccine (LAIV) in children with intermittent wheezing in an open-label field trial. Pediatr Infect Dis J May;27(5): Abbrose CS. Live attenuated influenza vaccine in children. Semin Pediatr Infect Dis Oct;17(4): Belshe R. Safety, immunogenicity and efficacy of intranasal, live attenuated influenza vaccine. Expert Rev Vaccines Dec;3(6): Belshe RB. Current status of live attenuated influenza virus vaccine in the US. Virus Res Jul;103(1-2): Pedro A. Live Attenuated Influenza Vaccine, Trivalent, Is Safe in Healthy Children 18 Months to 4 Years, 5 to 9 Years, and 10 to 18 Years of Age in a Community-Based, Nonrandomized, Open-Label Trial. Am J Epidemiol 2008;168:1343– Christopher SA. Current status of live attenuated influenza vaccine in the United States for seasonal and pandemic influenza. Influenza and Other Respiratory Viruses, 2, 193–202

15 Some facts (not for presentation)

16 Influenza vaccine during pregnancy (CDC Recommendations, sept 2009) – Can be administered in any trimester – Thimerosal free single dose vaccine recommended by CDC – Two doses at interval of days – Seasonal flu vaccine don’t protect against H1N1 flu – H1N1 vaccine & seasonal vaccine can be administered on the same day but must be on different site

17 Vaccine Efficacy A single measure of vaccine efficacy fails to capture the multidimensional protective effect of vaccination i.e prevent or reduce a number of outcomes, including laboratory-confirmed infection, symptomatic illness given infection, infectivity of infected individuals, or a combination of these. Vaccine efficacy (VE) is a measure of relative risk (RR) that generally takes the form VE = (1 – RR)

18 Live influenza vaccine and inactivated vaccine provided similar protection against laboratory-confirmed infection Four vaccine efficacy measures are : – Susceptibility (VES), – Symptomatic illness given infection (VEP), – Infection and illness (VESP), and – Infectiousness (VEI) – Combined (VEC) measure of the reduction in transmission in the entire population based on all of the above efficacy measures Vaccine efficacy for susceptibility (VES) – for live vaccine: 41% – for inactivated vaccine: 43% Efficacy for illness given infection (VEP) – Live vaccine had a higher efficacy for illness given infection – For live vaccine VEP was 67% and for inactivated vaccine VEP was 29%, although the difference was not statistically significant. Efficacy for infection and illness (VESP) – VESP for the live vaccine was higher than for the inactivated vaccine. Efficacy for infectiousness (VEI) estimates were particularly low for these influenza vaccines.


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