Prince Harry and Meghan Markle share new picture of Archie for his second birthday

Watch: 5 things you never knew about Archie Mountbatten-Windsor

Prince Harry and Meghan Markle have shared a new image of their son Archie as they call for donations to help ensure the coronavirus vaccine can be made available worldwide in honour of his birthday.

Archie Harrison Mountbatten-Windsor turned two on Thursday, celebrating his birthday in California where he now lives after Harry and Meghan stepped back from their senior royal duties.

Harry and Meghan initially shared a post on their Archewell website asking for donations to Gavi, the vaccine alliance, which buys coronavirus vaccines for countries which cannot afford them.

About two hours after their first post, they updated it with a new image of their son, who is set to become a big brother later this year when Meghan gives birth to their daughter.

Read more: Queen and Prince William wish Archie a happy second birthday

The image shows Archie with his back to the camera, looking up at a huge bunch of balloons.

He is dressed in a sweatshirt and jeans, and appears to have a pair of Nike trainers on.

The picture has been given a sepia tone in editing, making it harder to work out the details of the image.

Harry and Meghan have been very careful about how much information and what images have been released of their son, who has not been in the UK since November 2019.

They took legal action against a picture agency after photographs of him were taken while they were in Canada in January 2020, settling after the agency went into administration.

And they took action against unnamed paparazzi when drones were used to take pictures of the garden of the home they were staying in when they first moved to Los Angeles.

Read more: Archie Harrison turns two: A year in the life of Harry and Meghan's son

But when they were interviewed by Oprah Winfrey in March, they included some black and white home footage of Archie playing on the beach, and Harry revealed that he was enjoying taking him for bike rides, or to walk their dogs.

They also shared details of the latest words he was learning, with Meghan saying he liked the word "hydrate" which she found "hysterical".

Harry said he told people to "drive safe" when they left their home.

Archie appeared in one of the two photographs which the couple shared when they announced Meghan was pregnant with their second child, but his face was hidden as he was held in his mother's arms.

To mark Archie's birthday, Harry and Meghan thanked supporters for the donations which had been raised in previous years, but asked that this year they be focussed on the vaccination programme against coronavirus.

They also wrote an open letter in their capacity as co-chairs of the Vax Live concert, asking that the five biggest manufacturers of the vaccines increase the number of doses they are giving developing nations and speed up the rate of delivery.

Harry told James Corden during an interview that Archie had been joining him and Meghan in video calls to the Queen, and to Prince Philip before his death.

It's not known if Archie's birthday involved any video calls with relatives in the UK.

Harry returned for the funeral of the Duke of Edinburgh, but was in isolation for most of the trip. It was revealed after he returned that the conversations he had with family broke the ice amid ongoing tensions, but did not make any big strides forward.

Members of the Royal Family shared pictures of Archie on their social media pages to wish him a happy birthday, as has become a tradition for royals.

Watch: Harry and Meghan to celebrate as son Archie turns two