### Key messages
Vaccine misinformation on social media has strong effects on behaviour, and the evidence base for interventions to reduce these effects is limited, but better approaches to evidence generation are possible, say Kai Ruggeri and colleagues
Effective population level vaccination campaigns are fundamental to public health.123 Counter campaigns, which are as old as the first vaccines,4 disrupt uptake and can threaten public health globally.4 In 2019, public health researchers linked increases in measles cases with the proliferation of global anti-vaccine campaigns.5 Some of these campaigns originated offline but were later amplified and expedited through social media, resulting in real world harms.6 Though crises and genuine safety concerns can also lower vaccine uptake,78 the return of measles after aggressive anti-vaccine campaigns prompted the World Health Organisation to list vaccine hesitancy among the greatest threats to global health (box 1).14
Box 1
### Vaccine
Nigeria
New-york
United-states
Paulo-sergio-boggio
Emma-veitch
Alison-buttenheim
Valentina-cafarelli
Young-anna-argyris
Yuki-yamada
Kai-ruggeri
Ralph-hertwig
Mosokap-fallah