More than a fifth of the cohort received at least one dose of the pandemic vaccine, 46 percent of whom took their first dose during the first week of the vaccine’s availability. Researchers also found that more than half of the people in the group received only one dose of the pandemic vaccine, while a little more than 40 percent received two doses.
Researchers noted an increased likelihood of laboratory confirmed H1N1 infection during the first week after receiving the pandemic vaccine, with vaccine effectiveness at 112 percent, compared with patients who did not get the seasonal and pandemic flu shots. However, researchers did not observe significant effectiveness from the pandemic vaccine during the following eight to 14 days. Study data also revealed that participants who received only the 2009-10 seasonal flu vaccine were at an increased risk of contracting laboratory confirmed H1N1 infection.
Additional data revealed that vaccine effectiveness against H1N1-related hospitalization was estimated to be at 258 percent during the first week following receipt of the pandemic vaccine. However, researchers noted waning effectiveness during the following eight to 14 days. Patients who received only the seasonal flu vaccine were also at an increased risk of H1N1-related admission. The probability of hospitalization due to H1N1 infection was 18 times higher among patients aged 0 to 9, and about 10 times higher among patients aged 10 to 19. Patients aged 50 to 59 years also showed a two-fold increase in odds of being hospitalized compared with their older counterparts.Mass vaccination for influenza a failed strategy, scientists admit… it simply doesn’t reduce influenza-related hospital admissions at all – Dr. Eddy Bettermann MD