§ Lord Joplingasked Her Majesty's Government:
How long immunity from smallpox lasts in an individual who has been vaccinated one, two or three times at 10-year intervals; and [HL4359]
What proportion of the United Kingdom population is estimated to have a degree of immunity from smallpox as a result of having been vaccinated.
[HL4360]
§ Lord WarnerRoutine smallpox vaccination stopped in 1971. Fifty five per cent of the population were born before 1971 and the uptake of vaccine in the immediate years preceding this stoppage was 35 to 40 per cent. The estimate for the proportion of the current United Kingdom population now who have ever been vaccinated is about a third. No laboratory test to measure the immunological response, most likely to confer protection against smallpox, existed at that time.
A recent study⋆ from United States researchers has shown that the immunological response remains, in some degree, in 90 per cent of those vaccinated, but declines steadily over the decades since immunisation. It is not known whether, or to what extent, this protects against smallpox infection or development of disease. In that study, in those vaccinated one, two, three or more times, there was no correlation between the number of vaccinations received and the immunological response.
In the past, vaccination was required every three years for travel and yearly for those working close to smallpox cases.
⋆Duration of antiviral immunity after smallpox vaccination. Hammarlund, E et al, Nature Medicine 9 (9) September 2003.