ERF of H1N1 vaccination on Narcolepsy

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Scope

What is the ERF of H1N1 vaccination on narcolepsy?

Definition

Background

• First suspicion reported in May 2010.
• 15.8.2010 Swedish medicine agency reports time correlated cluster of narcolepsy with the vaccination programme.
  • 24.8.2010 THL recommends temporary halt in vaccinations until further information is available, except in cases where a doctor has explicitly assessed the risks.
• In 24.1.2011 57 cases of suspected vaccine related narcolepsy had been reported to THL.
  • 55 cases of narcolepsy and cataplexy symptoms, 2 cases of cataplexy symptoms.
  • 33 female, 24 male
  • Age: mean = 12, median = 11, min = 4, max = 37
  • Mean time after vaccination to onset of symptoms: 52 days
    • min = < 1d, max = 8 months
  • 54 out of 57 cases were 4 to 19 years old.
  • Total narcolepsy cases for 2010: 102
    • From which 62 in ages 4-19
• Besides Finland, only in Sweden and Iceland has narcolepsy been on the rise (out of 30 countries who widely used Pandemrix).
  • In Iceland incidence increased in the unvaccinated population also.

Data

In 5 to 19-year-olds

• From reviewed patient records the number of narcolepsy cases in subjects 5 to 19 years old in 2009-2010 was determined to be 60.
  • 52 cases in vaccinated subjects.
  • 8 cases in unvaccinated subjects.
  • ~70% of this age group were vaccinated.
  • Period of observation limited to 1.1.2009-16.8.2010, to rule out media impact (which was not significant according to some sensitivity analysis performed by the work group).
  • Period of observation of vaccinated subjects assumed from the start of the vacination programme (week 44?) until 16.8.2010.
• The odds ratio according to the report is 9.2 (4.5-21.4, 95% CI).

Adults

• 40 cases confirmed in 2010, which is less than on previous years.
  • 22 of the cases had been vaccinated.
  • ~43% of population vaccinated

Dependencies

• H1N1 vaccination coverage in Finland

Unit

OR is a dimensionless quantity.

Formula

• For calculating the erf based on data we have
  • Assumes that the vaccination program finishes instantly.

+ Show code- Hide code c(287786,302423,334636) -> pop c(215496,232704,178920) -> vac ((52/as.numeric(as.POSIXct("2010-8-16") - as.POSIXlt(44*7*24*60*60,origin="2009-1-1")))/sum(vac))/ ((8/as.numeric(as.POSIXct("2010-8-16") - as.POSIXct("2009-1-1")))/sum(pop-vac))

• For generating data from given mean and confidence intervals

+ Show code- Hide code logdstrm <- function(imean, isd) {log(imean)-0.5*log(1+isd^2/imean^2)} logdstrsd <- function(imean, isd) {log(1+isd^2/imean^2)} n <- 10000 Result <- rlnorm(n, logdstrm(9.2, 0.5*(21.4 - 4.5)/qnorm(0.975)), logdstrsd(9.2, 0.5*(21.4 - 4.5)/qnorm(0.975))^0.5) NERF <- data.frame(Age = rep(c("0-4 ","5-9","10-14","15-19","20-24","25-29","30-34","35-39","40-44","45-49","50-54","55-59", "60-64","65-69","70-74","75-79","80+"), each = n), obs = 1:n, Result = c(rep(1,n),rep(Result, 3), rep(1,13*n))) #op_baseWrite("opasnet_base", NERF)

Result

• 9.2 (4.5-21.4, 95% CI)

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See also

• Narcolepsy in Finland

Related files

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