A smartphone-based platform to send reminders or offering a gift card at the time of administering the first dose may help to ensure that people do not miss the second dose of a COVID-19 vaccine, experts have said.

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With the first vaccines reaching the public requiring two doses, there is a worry that some people may not take the second dose amid an aggressive disinformation campaign against vaccination. "There are several factors and behaviours that prevent many well-intentioned people from completing a two-step process, like that recommended for the COVID-19 vaccines," said Mark Fendrick from University of Michigan in the US.

"We need to provide everything necessary to support those who receive the first shot to make sure they complete their second dose." This lack of completion has been well established for other two-dose vaccines, like those that prevent less contagious and less lethal conditions, such as shingles, human papilloma virus (HPV), and hepatitis B.

The University of Michigan primary care physician and researcher said that vaccines that require more than one dose create additional behavioural and environmental challenges, including reports of side effects, false claims regarding vaccine safety, logistical barriers, and the politicisation of the programme, that may deter people from getting vaccinated or returning for their second dose. Health providers can distribute a card when giving first doses, to help educate patients about the vaccine and to encourage the pre-scheduling of second dose appointments.

A smartphone-based vaccine adherence support programme can also be added to optimise vaccine uptake, the University of Michigan said in a statement. "Smartphone apps and wearables already succeed in getting people to take their medicine, check their blood pressure or blood sugar, or even measure their heart rhythm," Fendrick said. Beyond automated reminders, a quick call or email from someone at a trusted source could do wonders, he said. In addition to customised messaging, Fendrick feels that small financial rewards like a $50 gift card would further increase vaccine uptake.

A vaccination campaign against the deadly coronavirus pandemic began in the US on December 14 as health workers rolled up their sleeves to get their first shots of the Pfizer-BioNTech vaccine. The vaccination regime submitted by Pfizer-BioNTech requires two doses of vaccine to be administered 21 days apart.