Background: UK COVID-19 lockdowns significantly affected primary care access and delivery. Little is known about whether lockdowns disproportionally impacted vulnerable groups, including people who misuse substances, people who have experienced domestic violence or abuse, those with intellectual disability, and children with safeguarding concerns.To evaluate the impact of UK COVID-19 lockdowns on primary care contact rates among vulnerable groups.Natural experimental design using all registered patients in the OpenSAFELY platform.With approval from NHS England, we conducted controlled interrupted time-series analyses on records from 24 million patients in England between September 2019 and September 2021.Pre-pandemic, primary care contact rates were 110.1 per 1000 patients per week. Following the initiation of the first lockdown (23 March 2020), there was a large reduction of 29–61 contacts per 1000 patients per week among vulnerable and general population groups. For patients with alcohol misuse, those aged ≥14 years with intellectual disability, and children with safeguarding concerns, this reduction was significantly more extreme than corresponding general populations (relative rate difference-23.8 [95% confidence interval {CI} =-39.8 to-7.7, P = 0.003],-24.6 [95% CI =-38.8 to-10.5,P<0.001], and-15.4 [95% CI =-26.9 to-3.8, P = 0.009], respectively). Following the final lockdown (29 March 2021), all groups had contact rates exceeding pre-pandemic rates (with increases more marked in vulnerable populations), except those only including children. Conclusion: Our results suggested a larger short- term impact of the first COVID- 19 lockdown on primary care contact for some vulnerable groups, compared with the general population, and differential impacts persisted through subsequent lockdowns and beyond for some vulnerable groups. There is a need to examine drivers of these differences to enable more equitable primary care access and provision.