The sportsman, 45, who is a goodwill ambassador for the charity, has urged families to ensure that their children are receiving routine vaccines to protect them against diseases such as diphtheria, measles and polio.
He stressed that the Covid-19 pandemic has ‘reminded us about the power of vaccines’.
In a video released ahead of World Immunisation Week, he said: ‘Covid-19 has made us all realise just how much we take for granted.
‘Vaccines work, they protect children and adults and they save millions of lives every single year. Vaccination is the reason that most of the world doesn’t have to live with deadly diseases like polio, measles and smallpox.
‘But there are still nearly 20million children around the world who are not getting the routine vaccines that they need to be safe.’
David is joined by the likes of Orlando Bloom, Olivia Colman and Jessie Ware, who will all be taking part in a series of online conversations regarding vaccines.
David has urged families to make sure their children are vaccinated against deadly diseases
As part of the vaccine drive, Unicef’s partners will each be donating $1 (72p) for every like, share or comment on social media posts mentioning the charity by name and using the hashtag #VaccinesWork until the end of April.
Henrietta Fore, Unicef executive director, said in a statement: ‘People all over the world are now getting a Covid-19 vaccine or anxiously awaiting the moment when they will.
‘Whereas today we all know Covid-19 vaccines are the best hope we have of resuming our normal lives, what remains “normal” for far too many children all over the world is no access to vaccines for any preventable diseases whatsoever.’
She added: ‘This is not a “normal” to which we should return.’
Nearly half the UK’s adult population has been vaccinated against Covid-19, and more than 11 million adults have had both doses.
It was also recently reported that children could get coronavirus jabs from September under Government plans to stop another wave over winter.