The results from the IVW showed genetic liabilities to critically ill COVID-19 were significantly causally associated with the increased risk of HER2-positive breast cancer (OR = 1.086, 95% CI = 1.015–1.162, P = .016), There were no causal associations between hospitalized COVID-19 (OR = 1.099, 95% CI = 0.985–1.226, P = .092) and HER2-positive breast cancer. Here, ERBB2 is linked to breast cancer.