1. A significant number of healthcare workers (HCW) are already immune to new flu strains, due to exposures from previous years, crossover immunity, and high levels of exposure. Thus a Spanish study found that 25% of its healthcare workers were already immune to swine flu prior to the 2009 epidemic. Vaccinating those with preexisting immunity may increase the risk of autoimmune reactions.
2. Prior year vaccinations may actually increase one’s risk of getting sick from flu, according to studies by Danika Skowronski and other Canadian researchers:
“… Because of limitations in study design and because they represented unexpected findings, we interpreted the results of this outbreak investigation as a paradoxical signal of possible concern-thought-provoking but inconclusive and warranting further evaluation. Canadian investigators thus embarked on a series of confirmatory studies using more rigorous methods and laboratory-confirmed outcomes through the summer of 2009, each of which corroborated findings from this initial outbreak investigation. In combination, these showed 1.4–2.5 fold increased risk of medically attended, laboratory-confirmed pH1N1 illness among prior 2008–2009 TIV recipients . An additional Canadian study using the linked Manitoba immunization registry and administrative databases has also shown similar findings of increased risk  (Dr Carole Beaudoin, Public Health Agency of Canada, personal communication). Thus, in Canada, 6 observational studies based on different methods and settings, including the current outbreak investigation, consistently showed increased risk of pH1N1 illness during the spring and summer of 2009 associated with prior receipt of the 2008–2009 TIV [4, 17]”
One reason may be that if you were previously vaccinated, you were less likely to develop a high antibody titre to a newer flu vaccine, according to researchers in Portugal. Consistent with these findings, the Dutch found a poorer response to adjuvanted swine flu vaccine in HCW who were vaccinated yearly for flu.
The Dutch researchers found that after being vaccinated for swine flu, antibody against swine flu persisted in 72% of health care workers who did not receive annual flu vaccinations, but in only 44% of those who got yearly flu shots.
HCW vaccinated yearly may therefore be at higher risk of disease when a serious influenza outbreak hits, as they are likely to mount a poorer response to vaccination than someone who is more vaccine-naive.
3. A recently published meta-analysis from Hong Kong of healthcare worker flu vaccinations and subsequent illness failed to show the vaccinations gave the healthcare workers any benefit:
“No evidence can be found of influenza vaccinations significantly reducing the incidence of influenza, number of ILI [influenza-like illnesses] episodes, days with ILI symptoms, or amount of sick leave taken among vaccinated HCWs.
There is insufficient data to assess the adverse effects after vaccination. There is no definitive conclusion on the effectiveness of influenza vaccinations in HCWs because of the limited number of related trials. Further research is necessary to evaluate whether annual vaccination is a key measure to protect HCWs against influenza infection and thus increase their confidence in the vaccine. In the mean time, the direction of promoting influenza vaccination to HCWs can be shifted from staff protection to patient protection, with accurate information to address concerns and misconceptions.”
4. How do you determine if a vaccine is “safe”? A study from Perth, Australia of vaccinated healthcare workers found that 1.3% of those who received seasonal flu vaccine sought medical attention for an adverse event temporally related to vaccination. That seems like a high rate for seeking medical attention; yet to the study author, it indicated the vaccine was safe.
What were the side effects due to this seasonal flu vaccine? A low rate of developing narcolepsy (a serious, lifelong disability) in adjuvanted swine flu vaccine recipients indicates to most people that the vaccine was not safe. Without knowing the precise type of side effects (and usually no one is looking for them very hard) it is impossible to assess safety from numbers such as % seeking medical attention.
In a Korean study, 11% of military healthcare workers reported fatigue after swine flu vaccine and 7% reported muscle pain. A whopping 32% had some type of systemic reaction. Being military, the participation rate was high; these are probably more reliable data than in most other studies.
A Japanese study of HCW receiving swine flu vaccine found that 1.3% had a severe adverse event within 7 days of vaccination, and 23% reported some type of systemic reaction. In Thailand, fatigue and malaise affected 24% of HCW after swine flu vaccination.
Note that the Koreans, Japanese and Australians got a vaccine that was very similar to that used in Finland and elsewhere in Europe, where it caused narcolepsy. None of these studies were designed to identify persisting adverse events such as narcolepsy. And the European narccolepsy cases were predominantly in the 5-20 year age group, generally outside the healthcare worker age range, which would cause them to be missed in any event.
I would conclude that vaccine safety remains uncertain, and that the range of long-terms effects from adjuvanted swine flu vaccine is probably not yet known. Will it ever be?