The COVID-19 pandemic has undermined capacity and efforts to address other health needs that are just as pressing as the virus itself, particularly in low- and middle-income countries (LMICs). Pressure on governments to act on COVID-19 now to save “immediately identifiable lives” rather than “statistical lives at risk”1 has had and will continue to have harmful short- and long-term consequences for other areas of health. This paper reviews the effects of vertical responses to COVID-19 on health systems, services, and people’s access to and use of them in LMICs, where historic and ongoing under-investments heighten vulnerability to a multiplicity of health threats. We use the term ‘vertical response’ to describe decisions, measures and actions taken solely with the purpose of preventing and containing COVID-19, often without adequate consideration of how this affects the wider health system and pre-existing resource constraints. Through four main sections focused on 1) characterising vertical response, 2) the drivers of broader health impacts, 3) evidence of impacts, and finally 4) suggestions for mitigation, we provide insight for actors in government, agencies, organisations and communities to design and implement more proportionate, appropriate, comprehensive and socially just responses that address COVID-19 without compromising other aspects of health.