University College London (UCL) reviewed 15 studies on contact tracing and found that apps do little good without a very high uptake and other measures running alongside them.
There are concerns that older people, already at much greater risk from coronavirus, will not know if they have been in contact with someone who tests positive because they do not have access to the technology.
According to the Office for National Statistics, (ONS) 40 per cent of the over-65s do not have a smartphone.
Dr Isobel Braithwaite, from UCL’s Institute of Health Informatics, said: “We should be mindful that automated approaches raise potential privacy and ethics concerns and also rely on high smartphone ownership, so they may be of very limited value in some countries.
“Too much reliance on automated contact tracing apps may also increase the risk of Covid-19 for vulnerable and digitally-excluded groups such as older people and people experiencing homelessness.”
The review, published in the Lancet Digital Health, found there is little evidence that apps work without other public health control measures such as large-scale manual contact tracing, physical distancing and the closure of indoor spaces such as pubs.
However, even with high levels of uptake – such as where 75-80 per cent of UK smartphone owners use the app, and 90-100 per cent of contacts adhere to quarantine advice – other methods of tracing would still need to be used, the report found.