The “lay health workers” in the Cochrane review by Lewin and colleagues (first published in 2005) [45] comprise CHWs at the less professionalized end of the spectrum, who “perform functions related to health care delivery, have been trained in some way in the context of the intervention, but have received no formal professional or paraprofessional certificate or tertiary education degree”. They could be paid or voluntary. Thus, this definition puts the CHW on the service delivery side (see Tension 1), but excludes those with more professionalized credentials In a review published by WHO in 2007 [46], it was stated that “CHWs …should: • be members of the communities where they work, • be selected by their communities, • be answerable to the community for their activities, • be supported by the health system but not necessarily a part of its organization, and have shorter training than professional workers”. The International Labour Organization (ILO) (2008) [47] described CHWs as: “provid[ing] health education and referrals for a wide range of services, and …support and assistance to communities, families and individuals with preventive health measures and gaining access to appropriate curative health and social services. They create a bridge between providers of health, social and community services and communities that may have difficulty in accessing these services”. This definition puts the CHW more definitively onto the PHC service delivery team, with the responsibility of providing information and support. The ILO also included in their definition that CHWs are “paramedical practitioners, occupations requir[ing] formal or informal training and supervision, recognized by the health and social services authorities”.

In the ILO’s new International Standard Classification of Occupations (ISCO-08) classification [47], there are several categories of workers that can be considered CHWs. Categorization according to the ISCO occupational groups and official job titles used in a jurisdiction do not always cohere. In some settings, the term “community health worker” or a similar term is used to refer to health workers who, according to the ILO ISCO classification, might more appropriately be referred to as nursing and midwifery associate professionals (ISCO 3221 and 3222) or paramedical practitioners (ISCO 2240). Conversely, health workers who have a role and profile consistent with ILO ISCO category 3253 (community health workers) may be classified and termed differently in a country (for example, community health officer, promoter, aide, educator, or volunteer). Categorization as community health workers (employment code 3253) is based on the health worker role, not on training or credentials, and listed tasks includes home visitation, giving information, supporting clients to access services, dispensing commodities, and monitoring and collecting data In 2013, the Global Health Workforce Alliance and its partners issued a joint statement [48] in which the term “community health worker” is used to refer to a wide range of both volunteer and remunerated health providers working within the community. In the important recent WHO guidance on policy and systems support for CHW programmes [3], the ILO 2012 language is cited, but revised slightly, providing somewhat more detail on the content of CHW work but—like the ILO document—WHO guidance focuses on health promotion tasks of CHWs, their integration into PHC teams, and linking the community with the health system

In a 2018 review, Scott and colleagues [49] described “community-based health workers” as “based in communities (i.e., conducting outreach beyond PHC facilities or based at peripheral health posts that are not staffed by doctors or nurses), … either paid or volunteer, … not professionals and … having at least some training, but < 2 years”. In 2017, Olaniran and colleagues [50] carried out a systematic review of definitions of CHWs and concluded that: (1) CHWs have an in-depth understanding of the community culture and language, (2) they are given standardized job-related training of a shorter duration than health professionals, and (3) a primary goal of their service is to ensure culturally appropriate health services to the community. The authors propose three categories of CHWs, based on educational prerequisites and duration of pre-service training: (1) lay health workers with little or no formal education who are given a few days to a few weeks of training, (2) those with some secondary education and subsequent informal training, and (3) those with some secondary education and training lasting from a few months to more than 1 year