Highly Predictive Model for a Protective Immune Response to the A(H1N1)pdm2009 Influenza Strain after Seasonal Vaccination
Fig 1
Serological response to A(H1N1)/pdm09 as function of age and number of strains that are sero-negative at baseline (NSSN) in the pilot and validation studies.
A) Pilot study: Non-response (HAI<10) and non-protection (HAI<40) to A(H1N1)pdm09 at day 21 post-vaccination are higher (30% and 50%, respectively) in old (>57 years) as compared to young (<31 years) vaccinees (12% and 12%, p = NS and p = 0.04, respectively). Furthermore, HAI titers at day 21 among responders are significantly (P<0.03) lower in old donors as compared to young donors. B) Pilot study: Non-response and non-protection to A(H1N1)pdm09 are higher (21% and 29%, respectively) in donors which were sero-negative to all 3 vaccine strains at baseline (NSSN = 3) as compared to donors which were sero-negative to H1N1 but sero-positive to the other 2 strains in the vaccine (NSSN = 1, 0%, p = NS). HAI titers among responders are not related to NSSN. C) Validation study: Non-response and non-protection to A(H1N1)pdm09 at day 21 post-vaccination are validated to be higher (38% and 46%, respectively) in old (>50 years) as compared to young (<50 years) vaccinees (7% and 10%, p = 0.02 and p = 0.01, respectively). However, HAI titers among responders are not related to age in the validation study. D) Validation study: Non-response and non-protection to A(H1N1)pdm09 are higher (29% and 33%, respectively) in donors which were sero-negative to all 3 vaccine strains at baseline (NSSN = 3) as compared to donors which were sero-negative to H1N1 but sero-positive to the other 2 strains in the vaccine (NSSN = 1, 0% and 11%, p = 0.04 and p = 0.05, respectively).