Photo Credit CDC
# 5897
Whenever there is a hint or a suggestion that a vaccine might have caused some sort of serious side effect, it invariably becomes big news.
Even when the reports are preliminary, and the evidence less than rock solid, these stories often end up on the front pages of newspapers and quickly become fodder for the anti-vaccination brigade.
When more reassuring vaccine studies come out, they rarely get that kind of media play, since it isn’t the sort of thing that sells newspapers.
Case in point:
A little over a year ago GSK’s Pandemrix vaccine was associated with a perceived increase in narcolepsy among children and adolescents in Finland. For early coverage of this story, you may wish to revisit Finland Suspends Use of Pandemrix Vaccine and EMA To Review Pandemrix Vaccine, both of which I wrote in August of 2010.
Despite some conflicting and incomplete data the European Medicines Agency issued a statement last July recommending:
In persons under 20 years of age Pandemrix to be used only in the absence of seasonal trivalent influenza vaccines, following link to very rare cases of narcolepsy in young people.
Finland also convened a Narcolepsy Task Force (see Finland: Task Force Report On Pandemrix-Narcolepsy Link) that confirmed an association – as yet unexplained – between receipt of the vaccine and an increase in narcolepsy in children between the ages of 4 and 19.
Complicating matters, more than a dozen countries reported an increase in narcolepsy during the 2009 pandemic, even those where the adjuvanted vaccine was not used.
You can find details on one such study in Stanford Study Finds Influenza – Narcolepsy Connection that linked narcolepsy not to the vaccine . . . but to infection by influenza virus itself.
Confused yet?
Alas, science isn’t always neat and tidy. Good studies take time, and we don’t always get consistent results.
Today, we’ve another study that appears in the BMJ that is a bit more reassuring on the safety of the Pandemrix vaccine, but fails to answer the question of narcolepsy.
It is called:
Neurological and autoimmune disorders after vaccination against pandemic influenza A (H1N1) with a monovalent adjuvanted vaccine: population based cohort study in Stockholm, Sweden
OPEN ACCESS
Carola Bardage, epidemiologist, Ingemar Persson, professor of pharmacoepidemiology and senior expert, Åke Örtqvist, county medical officer and associate professor, Ulf Bergman, professor of pharmaco-epidemiology and clinical pharmacologist, Jonas F Ludvigsson, paediatrician and epidemiologist, Fredrik Granath, senior biostatistician
This was a population based cohort study conducted in Stockholm, Sweden during the 2009 pandemic where 1,024,019 people were vaccinated with the Pandemrix vaccine and 921,005 remained unvaccinated.
Using the detailed healthcare registers for Stockholm County Council, researchers tracked all admissions to hospitals and visits to specialists for autoimmune or neurological diagnoses.
The conditions flagged in this study included:
- Guillain-Barré syndrome
- Bell’s palsy
- multiple sclerosis
- polyneuropathy
- anaesthesia or hypoaesthesia
- paraesthesia
- narcolepsy
- rheumatoid arthritis
- inflammatory bowel disease (ulcerative colitis, Crohn’s disease)
- type 1 diabetes
This study further divided this cohort into those who received the vaccine within the first 45 days of its availability, and those who received it later. Those in high risk groups, with comorbid conditions, were more likely to be vaccinated during the first 6 weeks of the vaccination campaign.
The results (which are far more detailed in the open access report) indicated:
Conclusions
Results for the safety of Pandemrix over 8-10 months of follow-up were reassuring —notably, no change in the risk for Guillain-Barré syndrome, multiple sclerosis, type 1 diabetes, or rheumatoid arthritis.
Relative risks were significantly increased for Bell’s palsy, paraesthesia, and inflammatory bowel disease after vaccination, predominantly in the early phase of the vaccination campaign.
Small numbers of children and adolescents with narcolepsy precluded any meaningful conclusions.
The report summary states:
What is already known on this topic
-
Studies are lacking on adverse events (except for narcolepsy) with any of the three vaccines used in the European Union against H1N1 during the pandemic period
-
Available data are limited to case series or highly selected populations with short follow-up or no control group
What this study adds
-
Excess risks for Bell’s palsy, paraesthesia, and inflammatory bowel disease after H1N1 vaccination with adjuvanted Pandemrix in Sweden were small but significant among more than one million vaccinated, but only in high risk groups targeted for early vaccination and who were likely to have earlier comorbidity
-
The risk of Guillain-Barré syndrome, multiple sclerosis, type 1 diabetes, and rheumatoid arthritis remained unchanged
-
Small numbers of children and adolescents with narcolepsy precluded any meaningful conclusions
While the low number of children and adolescents with narcolepsy may have precluded making any firm conclusions, their scarcity is nonetheless a bit reassuring.
The authors suggest that the small, but statistically significant increase in Bell’s palsy, paraesthesia, and inflammatory bowel disease among the early recipients of the vaccine may be partly, or perhaps entirely, explained by the higher number of high risk patients in that cohort.
We are still left with the mystery of what caused the increase in narcolepsy reported in Finland, of course. And there will no doubt be additional studies that will look at the safety of the Pandemrix vaccine in other regions.
But for now, as the authors state, the news is `reassuring’.
For previous reports on the safety of (adjuvanted and unadjuvanted) flu vaccines, you may wish to revisit.
IOM Report On Vaccine Safety Concerns
BMJ: No Substantial Link Between Flu Vaccines And Guillain-Barre Syndrome
Lancet: Immunogenicity and safety Of Adjuvanted Flu Vaccines
NEJM: Study On China’s H1N1 Vaccine Safety
Harvard Study Reaffirms Safety Of Flu Vaccine
