A total of 6242 HCW vaccinated with the 2009 pandemic vaccine and 7549 vaccinated with the 2010–2011 seasonal influenza vaccine were enrolled and had a valid email address. () Among them 53% and 70% respectively responded to the two surveys and 80% and 83% responded to at least one survey. In 2009, demographic information was collected at only at one site whereas all sites collected it in 2010–2011. In both years, about three quarters of participants were women. The age ranged from 16 to 87 years with about two thirds being between 30 and 60 years old while fewer than 8% were 60 years and older. The overall mean age was 39 years in 2009 and 41 years in 2010–2011. Compared to the active population in Canada, there was an over-representation of women but the mean age (40 years) was similar. 
For both years, about 12% were physicians, 19–27% were nurses, 10–16% were other types of health professionals (pharmacists, physiotherapists, etc.) and 44%–45% were administrative or other types of workers. In 2010–2011, 91% (95% CI: 90.6, 92.0) of participants had been vaccinated against pandemic influenza the year before and 91% (95% CI: 90.0,91.5) had received seasonal influenza vaccine at least once previously.
Characteristics of the health care workers vaccinated with the monovalent 2009 AS03-adjuvanted pandemic vaccine or the 2010–2011 trivalent inactivated seasonal vaccine.
Among HCW with a valid email address, for the 0–28 day follow-up, 508 (8.1%; 95% C.I: 7.5, 8.8) in 2009 and 386 (5.1%; 95% CI: 4.6, 5.6) in 2010–2011 reported on their electronic survey at least one event for which they missed work or had a medical consultation. After contact from research nurses to validate the events, 85 of the 553 events reported after the 2009 pandemic vaccine were excluded for the following reasons: 49 were erroneously reported and did not result in a medical consult or work absenteeism (main outcome) and 36 could not be validated either because the HCW did not want to divulge information about the event or the HCW was not reached. In 2010–2011, 61 of the 412 reported events were excluded after nurse follow up: 15 did not meet the criteria for the main outcome and 44 could not be validated. After these exclusions, there were 440 HCW (7% of participants; 95% CI: 6.4, 7.7) who reported 468 AEFIs after the pandemic vaccine and 328 HCW (4.3%; 95% CI: 3.9, 4.8) reported 339 AEFI after the seasonal vaccine. In both years about 80% of cases missed work for their AEFIs and about 50% consulted a physician.
As shown in , in the 28 days post vaccination, the 2009 pandemic vaccine was associated with significantly more local reactions causing work absenteeism or medical consultation than the 2010–2011 seasonal vaccine (0.96% vs. 0.03%, p<0.0001). Fever alone was significantly less frequent with the 2009 pandemic vaccine (0.12% vs. 0.86%, p<0.0001) but general malaise with or without fever was similar with both vaccines. Upper respiratory tract infection was the most commonly reported health problem during both years and was significantly more frequent with the pandemic than the seasonal vaccine (4.6% vs. 2.6%, respectively, p<0.0001). Similarly, there was more gastroenteritis reported after the pandemic vaccine than the seasonal vaccine (1.8% vs. 0.4%, p<0.0001). During the 8 to 28 day follow-up period, headache/migraine and urinary problems were reported less frequently after the 2009 pandemic vaccine than with the 2010–2011 seasonal vaccine ().
New health problem or the worsening of an existing condition of sufficient significance to cause a medical consult and/or work absenteeism by follow-up period and type of influenza vaccine.
Only 3 of the 12 HCW (8 in 2009, 4 in 2010) who reported allergic symptoms 0–7 days post vaccination had their symptoms occur shortly after vaccination and all 3 had received the adjuvanted pandemic vaccine. The first case developed anaphylaxis within 30 minutes post-pandemic vaccine with generalized urticaria, swelling of the mouth and nausea. The case received adrenaline and was transferred to the emergency room. The second case developed urticaria starting 30 minutes post-vaccination followed by throat tightness an hour later. The case was transferred to the emergency room where antihistamine, corticosteroids and antacid were administered. The case was kept under observation for 4 to 5 hours and then discharged. The last case presented at the emergency department with generalized urticaria and swelling of the lips which started 5 hours post-vaccine.
In the 28 days after the 2009 pandemic vaccine, seven HCW reported paresthesia described as numbness or tingling of sufficient significance to require consultation or work absenteeism. This compared with zero reports following the 2010–2011 seasonal vaccine. () While two HCW reported paresthesia in their vaccinated arm, four reported numbness and tingling in their lower limbs and one reported it in both upper limbs. For five of the seven HCW, symptoms started 0–7 days after vaccination.
Paresthesia of sufficient enough to cause work/school absenteeism or a medical consultation after the 2009 pandemic vaccine.
No HCW reported diagnoses compatible with an auto-immune disease during the 28 days after receipt of the adjuvanted pandemic vaccine. In that same period, there were two SAE (hospitalization, life-threatening event, disability or stillbirth/congenital anomaly) reported for a rate of 0.32 per 1000 HCW (95% CI: 0.04,1.16) immunized. One was the first case of anaphylaxis described above. The second SAE occurred in a 55–60 year old woman with a history of diabetes and hypertension who was hospitalized for an atrioventricular block that required a pacemaker. In the 28 days after the 2010–2011 seasonal vaccine, no SAE were reported.
In the six-month follow-up after the 2009 pandemic vaccine, emails were sent to the 4,812 HCW from the Quebec City site (77% of total 2009 participants) and 3,064 (63.4%) responded. Among 68 (2.9%) participants who initially reported a SAE in the one to six month period after their pandemic vaccination, 33 were excluded after follow up by a nurse: 19 had problems that did not meet the SAE criteria, 11 had erroneously responded that they had a SAE and 3 could not be reached despite numerous attempts thus no information was available about their problem. Among the 35 HCW who met the criteria for SAE, 25 (57%) had been hospitalized, 8 (20%) reported a life-threatening event and 9 (23%) had an event resulting in persistent or significant disability/incapacity. There were no congenital anomalies/birth defects reported. Six HCW had conditions that met two criteria for a SAE with hospitalization for respiratory infections (3), hospitalization for gastrointestinal infections (4) and hospitalization for cutaneous infections (2) occurring most frequently. Otherwise the reported diagnoses affected only one patient, suggesting no cluster of SAE associated with the vaccine. ().
Serious adverse events (SAE) reported for the period 1–5 months after the 2009 AS03-adjuvanted monovalent pandemic vaccine.