Mobile vaccination units substantially increase COVID-19 vaccinations: evidence from a randomized controlled trial

Background Governments around the world used mobile vaccination units (MVUs) to increase COVID-19 vaccine uptake, but the causal effect of MVUs has not yet been evaluated.Methods In a randomized controlled trial (RCT) with 20 Swiss communities (10 treatment, 10 control) in August 2021, MVUs were sent to treatment communities for 4 hours on a single day. The experimental sample comprises 20 414 adults who were unvaccinated against COVID-19 at this point. The researchers designed the RCT and the government introduced the idea to test the effectiveness of MVUs and was responsible for administering the vaccines.Results The vaccination rate in the sample of the treatment group surpassed the rate in the control group by a factor of 3.4 (+9.0 percentage points) over 3 weeks. The increase was present and highly statistically significant for women, men and for all age groups. We found no evidence of cannibalization of vaccinations at other service locations.Conclusions The offer of MVUs is highly effective in raising vaccination rates, even at a later point in the vaccination campaign. The absence of cannibalization effects suggests that MVUs reach more people overall, not just faster.