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Occup Environ Med. 2007 July; 64(7): 490–491.
PMCID: PMC2078470

Sickness absence of multivaccinated employees at Porton Down: a retrospective cohort study

Concerns have been raised about the effects of multiple vaccinations on long‐term health, particularly in military personnel, but are unproven.1 Animal models have shown no significant relations between multiple vaccination and reported ill health in service personnel.2,3,4

The Defence Science and Technology Laboratory (Dstl) conducts scientific research for the UK Ministry of Defence; staff working with pathogens or serving abroad are offered appropriate vaccinations. We investigated whether increased sickness absence, as a measure of morbidity, was associated with multiple vaccinations in Dstl staff working at Porton Down.

A retrospective cohort study was undertaken following ethical approval. Group 1 comprised multivaccinated staff employed for 2–38 years who had, in adult life, received four or more different vaccines (including for anthrax, plague, botulism, tularemia and smallpox). Controls (Group 2), who had received three or fewer vaccines (but not anthrax, plague or botulism) as adults, were matched for gender, age, grade and service length. Both groups had received standard childhood immunisations. Total sick leave over the employment period was obtained from personnel records. Absences considered unrelated to vaccination (for example, surgery) were excluded (“filtered” leave).

Group 1 received a mean of 5.6 different vaccines (median 5, range 4–11); 35 individuals had received five different vaccines, seven had received 10 or more. Total injections ranged from 6–100. There was no difference between the two groups for average annual total sick leave but filtered sick leave was significantly less in Group 1 (table 11).). Sick leave in both groups decreased in a similar fashion with individual length of employment, despite the fact that average annual sickness rates for all staff increased over the period studied (data not shown).

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Table 1 Sick leave in Group 1 versus Group 2

In conclusion, there was no excess sickness absence among staff receiving multiple vaccinations (including repeated doses of potential biological warfare agent vaccines) compared to matched controls. Sickness rates did not increase with the number of different vaccines received or total number of injections. These data are consistent with experience in the US5 and provide additional evidence against multiple vaccinations contributing to long‐term ill health.


This study was supported by the Veterans Policy Unit of the Ministry of Defence.


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