This research investigated whether people who are generally helpful in their everyday lives (for example, by donating blood or volunteering) were also more cooperative during the COVID-19 pandemic. We created a "prosocial phenotype" score based on four real-world helpful acts. We then tested two main ideas in a large UK study (3,000+) across eight periods of the pandemic. First, we found that these prosocial individuals were especially good at following health guidelines, like social distancing, but only when the rules were confusing and unclear. When government instructions were strict and simple, everyone followed them similarly. Second, while the main reason anyone got vaccinated was to protect themselves, prosocial people were significantly more likely to also be motivated by a desire to protect others and help achieve herd immunity.