Brisk walks help flu vaccine work longer

1 May 2010

CLINICAL BOTTOM LINE:

Sedentary adults aged 60+ having influenza vaccinations should be advised that aerobic exercise – e.g. brisk walking three times per week for 45-60 minutes – increases the duration of seroprotection, in addition to its other cardiac benefits. The effect on incidence of influenza remains unknown.

CLINICAL SCENARIO:

Older people have lower rates of protective seroconversion with vaccination. As a certified vaccinator you are always looking for ways to enhance the effect of vaccination for over-60-year-olds, and to better protect those who receive the vaccination. In the course of casual browsing of Best Evidence for Nursing, you stumble across just such a paper.

QUESTION:

Among older patients, does the addition of exercise increase the effectiveness of influenza vaccination?

SEARCH STRATEGY:

Nil – browsing the websites Evidence Update and Best Evidence for Nursing.

CITATION:

Woods JA, et al. Cardiovascular exercise training extends influenza seroprotection in sedentary older adults: the immune function intervention trial. J Am Geriatr Soc 2009; 57:2183-91.

STUDY SUMMARY:

Two-arm parallel group, outcome blinded, randomised controlled trial conducted in the United States. Sedentary adults aged over 60 years recruited through newspaper and local media advertising and contacts with local health facilities over three influenza seasons (2003-2005). Inclusion criteria were: ability to participate in an exercise programme, clearance from a medical practitioner, non-smoker, BMI 22-38, currently either not in or planning to be involved in a weight reduction programme and sedentary (no planned or structured exercise more than once per week in the previous six months). People were excluded if they had a history of cancer, using immunosuppressant drugs, uncontrolled diabetes, severe arthritis, clinical depression, impaired cognitive function, systemic reactions to vaccinations, history of alcohol or drug abuse, or abnormal blood count or metabolic values. 556 people were screened, 186 meet the inclusion criteria and 160 were randomised. Four months after the start of the intervention each participant received trivalent vaccination (Fluzone, Aventis Pasteur) for H1N1, H3N2 and influenza B using CDC-recommended method. Variants for H3N2 were Panama, Fujian and New York. Variants for influenza type B were Hong Kong and Shanghai. Blood samples were obtained before vaccination and at three, six and 24 weeks after vaccination.

Intervention (n=78):

Cardio group received supervised aerobic exercise starting at 45-55% VO2Max for 10-15 minutes per session three days per week, increasing to 60-70% VO2Max for 45-60 minutes per session within three months. Mode of exercise varied (walking, cycling, stair climbing or elliptical machines), but included brisk walking at least twice per week.

Control (n=82):

Flex group received supervised large muscle stretching and balance exercises using low level resistance devices for 75 minutes per session two days per week. Intensity was assessed as below 20% VO2Max and cardiac training effect was minimised.

Outcomes:

Primary outcome measure was influenza vaccine response as measured by haemaglutination inhibition (HI) anti-influenza antibody titre and seroprotetcive responses (HI titre ≥40). Secondary measures included cardiovascular fitness, body composition, respiratory tract illnesses and adverse events.

Validity:

Eligible patients described as being randomised, but generation of allocation sequence not described, although methodology referenced. Allocation concealment not reported, although investigated and described as being blinded to group assignment. Follow-up for 24 weeks. Loss to follow-up: 10 patients overall with 5% lost in Cardio group and 12% lost in Flex group. Analysis was by intention-to-treat, but participants lost to follow-up excluded from analysis. Blood samples labelled with code to ensure outcome assessors blinded to group allocation. Participants appear to have been treated equally and groups balanced at baseline. Overall impression – a reasonable quality study with some deficiencies in reporting of methods.

RESULTS:

Participants were aged 60-83 years with mean age of 69 years. 62% were female. Adherence to supervised intervention similar in both groups (82% vs 83%). There were no significant differences in HI titres at three and six weeks, but significantly more participants with seroprotection in the Cardio group at 24 weeks (see table). There was no difference between the groups for self-reported respiratory illnesses or adverse events.


 

  TABLE RESULTS WITH 95% CONFIDENCE INTERVALS

 

Intervention

Intervention effects

Number needed to treat

(95%CI)

Cardio

(n=74)

Flex

(n=70)

RR

(95%CI)

Absolute effect

(95%CI)

 

H1N1 titre ≥40

43.2%

21.4%

2.0
(1.6 to 2.6)

21.8%

(7.0 to
36.6%)

5

(3 to 14)

H3N2 titre ≥40

55.4%

38.6%

1.4
(1.1 to 1.8)

16.8%
(0.8 to 32.9%)

6

(3 to 131)

Type B

45.9%

35.7%

1.3
(0.98 to 1.69)

10.2% (-5.7 to 26.2%)

NS

 

 

 

 

 

 

 

 

COMMENTS:

No sample size calculation reported. Trial funded by US National Institutes of Health and registered on http://clinicaltrials.gov.

All exercise supervised, but no reason to conclude that effecced by unsupervised exercise of similar intensity and duration. Inclusion of brisk walking as main means of aerobic exercise increases generalisability of results.

Reviewer: Dr Andrew Jull, RN PhD, Nurse Advisor – Quality, Auckland District Health Board and Associate Professor (The University of Auckland school of nursing).