New review

Can exercise before vaccination help avoid flu? 

Plain language summary  

Can exercising before vaccination reduce numbers of adults who get flu or develop complications?

Review question
We looked at whether exercise before influenza (flu) vaccination can decrease numbers of adults who develop flu and reduce complications.

Background

Exercise can change immune response. Flu is an infectious virus estimated to affect three to five million people worldwide each year. Seasonal flu vaccination, which acts on the immune system to protect people from infection, is common in many countries.

Search date

We searched the literature up to November 2015.

Study characteristics
We looked at six studies that involved 599 people aged between 18 and 80 years that assessed exercise before flu vaccination. Exercises included walking or using a treadmill (endurance) and biceps curls and lateral raises (resistance) activities that ranged from 25 to 50 minutes per session. People in five studies did one session of exercise on the day of vaccination; in one study people exercised eight weeks before vaccination. Exercise was supervised in three studies. People not undertaking exercise (control group) were assessed after periods of quiet rest.

Study funding sources

Three studies did not report study funding sources; one received support from a drug company that donated flu vaccine, one from a professional society, and another from government agencies.

Key results
We found no differences in numbers of people who caught flu or developed complications between people who exercised and those who did not before flu vaccination. Only one study reported how many people developed flu after exercise and vaccination. No studies reported complications related to flu; only one reported adverse events. None reported numbers of working or other days lost due to flu. No beneficial differences were reported between exercise and no-exercise groups before vaccination.

Small numbers of people who were involved in the studies, limitations in study design, and different exercise types meant we were unable to draw robust conclusions about any benefits of exercise before vaccination. There appears to be no benefit or harm from exercising before receiving flu vaccination.

Quality of evidence
Evidence quality was very low or low. More robust study designs that include enough people to enable assessment and analysis of findings may help to determine if exercise before vaccination can reduce numbers of people who develop flu or complications.

Author's conclusions

We found that exercising before influenza vaccination is neither beneficial nor harmful. Small number of people in each included study, many types of exercises, and focus on blood examination instead of participant-centred outcomes strongly influenced our findings.