Adverse Events Following Immunization (AEFI) Quarterly Report for 2015 – Q1

Safety assessment summary for this Quarter:

• No significant vaccine safety concerns were identified in quarter 1 of 2015.
• All serious cases were reviewed and most found either to be expected (based on known vaccine-related adverse reactions and listed in the Canadian Immunization Guide and Product Information) or to have alternate explanations and not related to vaccination.
• As in previous quarters the total count of AEFI reports received was lower than that seen in previous quarters reflecting a gap in reporting from jurisdictions that are implementing new electronic reporting systems.

Vaccines are closely monitored in Canada at all phases of the vaccine product 'life cycle' from discovery through market authorization (pre-market) and beyond, as people begin using them (post-market).  Many stakeholders are involved in various activities related to vaccine safety assessment and monitoring including the federal government, provincial, territorial and local public health authorities, health care providers, vaccine industry and the public.  The Public Health Agency of Canada (the Agency) conducts vigilant post-market safety surveillance through a national reporting system, the Canadian Adverse Events Following Immunization Surveillance System (CAEFISS).

The primary purpose of vaccine post market surveillance is to detect safety concerns.  These concerns include a possible increase in the severity or frequency of expected reactions, or occurrence of one or more unexpected events (i.e. an event that is not consistent with Canadian product information or labelling). This allows immunization providers and public health immunization program providers to take public health action at the level of the:

• individual (e.g. further investigation to confirm a diagnosis and determine possible causes, consultation to rule out allergy to one or more vaccine components, or evaluate whether or not to give subsequent doses of a vaccine), and/or
• immunization program (e.g. investigation of a cluster of adverse events, review of procedures to ensure that vaccine storage requirements have been strictly followed, or consider a change in policy to adopt a less reactogenic vaccine).

The Agency also shares adverse event following immunization (AEFI) data with Health Canada, the vaccine regulator in Canada, to enable regulatory action related to vaccines marketed in Canada.  These actions may include issuing communications to immunization providers or the public regarding the safety concern or requiring additional information or investigation by the vaccine distributor.

Vaccine safety surveillance reports summarizing CAEFISS data are released by the Agency on a routine basis. The Quarterly Reports  summarize all reports of adverse events following immunization (AEFI) received by the Agency  from Jan 1st to March 31st (Quarter 1), Apr 1st to June 30th (Quarter 2), July 1st to Sept 30th (Quarter 3) and Oct 1st to Dec 31st (Quarter 4), regardless of the date the vaccine was actually given. In addition, the Quarter 4 Report provides cumulative data spanning the entire year and contains a more detailed review of any concerns that may have been observed in the earlier reports.

In order to compare data from year to year, each quarter's data are shown along with an average of several prior years' quarterly data.

Notes on interpretation: An AEFI is defined as "any untoward medical occurrence which follows immunization and which does not necessarily have a causal relationship with the usage of the vaccine. The adverse event may be any unfavorable or unintended sign, abnormal laboratory finding, symptom or disease".  AEFI reports submitted to the Public Health Agency of Canada represent a suspicion, opinion or observation by the reporter as opposed to an assertion or proof that the vaccine may have caused the event. For most events a clear causal relationship is difficult to establish. Additional limitations to AEFI report data include varied reporting standards and underreporting, lack of certainty regarding the diagnostic validity of a reported event, missing information regarding other potential causes and other reporting biases. In short, this information should not be used to estimate the incidence of adverse events. 

Results highlighted for Quarter 1 of 2015

Cumulative counts included in this Quarterly Report (Q1) include reports received from Jan 1st to Mar 31st and comparisons are made to the average number of reports received in the same quarter over the previous four calendar years (2011-2014).  The reports analysed for 2015 were extracted from the CAEFISS database on 15 May,-2015 and for 2011-2014 on 29-April-2014 by the Public Health Agency of Canada (the Agency).

Frequency of serious and non-serious AEFI Reports by Age Group

There were a few changes in age distribution for serious AEFI reports received in Q1 for 2015 relative to previous years.  Notably, as shown in Table 1, the total of all serious reports for children 1 to less than 2 years of age was higher in the first quarter of 2015 than the previous 4 year average (26 versus 13). This change was related in part to an increasing use of new hexavalent vaccines (DTaP-IPV-HB-Hib). New vaccines typically have increased reporting rates. (see Table 3 below).

For non-serious AEFI reports, the age group distribution was similar in Q1 in 2015 to previous years for Q1.

Most common vaccines identified in Adverse Events Following Immunization (AEFI) Reports

Table 3 lists the most commonly implicated vaccines among AEFI reports received for Q1 of 2015 relative to the 2011-2014 average reports received for the same quarter.  The most notable change in the 1st quarter of 2015 relative to previous years was a higher number of serious AEFI reports following hexavalent vaccine, along with meningococcal and MMR vaccines. Hexavalent vaccines have still only recently emerged and thus they have fewer historic reports, and MMR vaccine distribution has likely increased as a result of recent outbreaks drawing attention to the importance of catching up with the vaccine.

Figure 3 provides a cumulative summary of the most commonly implicated vaccines among AEFI reports received by the Agency during the 1st Quarter of 2015 (Jan 1st to Mar 31st) compared to the average in 2011, 2012, 2013 and 2014 for the same time frame.   As already noted in previous reports there was a trend for a lower frequency of non-serious adverse event reports for most commonly administered vaccines relative to the previous four years.  The reason for the lower numbers is primarily accounted for by delays in reporting from jurisdictions still in the process of initiating new electronic AEFI reporting infrastructures. These will reflect increases in subsequent reports and will be explained at the time.

The main reason for reporting serious (SAE) and non-serious (non-SAE) AEFI for Q1 of 2015 compared to the 2011-2014 average for Q1 is shown in Table 4.

Figure 4 provides a cumulative summary of reports received from the beginning of the year to the end of Q1 (Jan 1st - Mar 31^st) compared to the average in 2011-2014. As noted previously, the total numbers of non-SAE reports were less than previous years. The most frequently reported non-SAE were reactions at or near the vaccination site, rash as the only event, allergic or allergic like events and systemic events.

Serious Adverse Events Following Immunization (SAE) Reports received

The type of serious adverse events (SAE) reported are described below.  Table 5 summarizes the type of SAE reported in Q1 of 2015 compared to the 2011-2014 average. Figure 5 provides a cumulative summary of the same data collected from the start of the year to the end of the quarter  (Jan 1 - Mar 31st) in 2015 compared to the average in 2011-2014.

There were a total of 70 SAE reports in Q1 of 2015 (9.4% of 744 reports total). The average for Q1 from 2011 to 2014 was 58 serious reports (7.2% of 977 reports total). As noted in previous reports, the single most common reason for reporting SAEs in Q4 were seizures usually accompanied by fever. The only increase by category of SAE was for systemic events, but an investigation of these did not reveal any clustering by event, age or vaccine.