I'm in a UK Covid vaccine trial – should I also accept a 'real' jab?

I had two excellent pieces of news this week. They left me feeling utterly wretched.

First, my turn came up for the AstraZeneca vaccine against Covid. I was told I could have my first jab on Thursday.

But I am a guinea pig in the trials of the Novavax vaccine, which has yet to be approved anywhere. I was assured when I signed up that, if offered an approved vaccine, I would be in no worse a position than if I had not signed up. But once offered an approved vaccine, I needed to be “un-blinded”. Half the guinea pigs had the trial vaccine; the other half had a placebo. Which half was I in?

The research manager at the Royal Free hospital in Hampstead, north London, gave me my second piece of good news. I have had two doses of the trial vaccine. I’m probably immune already.

Related: Is it worth carrying on as a guinea pig, if a vaccine has already been found? Francis Beckett

Only then did I realise that I had been hoping to be told I had the placebo. Then it would be simple. I would drop out of the study and turn up for my AstraZeneca vaccine on Thursday.

As it was, it was far from simple. I could still drop out of the study and take the AstraZeneca vaccine. There are no studies that suggest any harm can come out of mixing vaccines, or having four doses in my body instead of two.

But that may be simply because there are no studies. At all. No one has looked at what the effect on the body might be. Because of this lack of knowledge, the Medicines and Healthcare products Regulatory Agency (MRHA) advises those in a vaccine study not to take an approved vaccine.

So I should cancel my appointment. But when I have the chance of an approved vaccine, why would I turn it down because I have a vaccine that is not yet approved, and may conceivably not work?

All right, Novavax phase 1 and 2 studies were good, but they were small samples. The big study, of which I am a part, is phase 3, and they expect results early next month. “Anecdotally, it works,” the researchers told me. “There’s no reason to believe it’s not as good as the approved vaccines.”

I had been looking forward to getting the approved vaccine, and rather assuming I would take it. I so want certainty.

I’m not alone. A WhatsApp group of some contemporaries, friends from my time as a student at Keele University at the end of the 60s, was behaving like a group of excited children last week. “Mine’s Tuesday!” “I’m getting it next Monday!!!” The one who hasn’t had the summons yet sounds like a schoolgirl denied the class outing. And I’m thinking of turning mine away! I must be mad.

Related: At 75, I've volunteered for a Covid vaccine trial. It could set people free

I haven’t coped well with living like a mole. I’m getting small irritations out of proportion. I pine for France. Even when this is over, my visits to France will never be free and easy as they used to be. The virus and Brexit seem to merge into one ugly troll which diminishes my world.

I keep busy. My play about Clement Attlee, due to return to Upstairs at the Gatehouse, in Highgate, London, in April, has been cancelled three times – I hope to get it on in the summer. I’ve written a new play, though heaven knows when theatres will reopen. I’ve published a collection of my short stories, and written a few articles about things I care about, mostly for the New European.

What should I do? The researchers are keen for me to stay in the study – it throws the results when people withdraw. But I’m putting myself first this week.

I asked my GP, who is kind and sensible. She talked me through the dilemma, but she didn’t know the answer, any more than I did. She reassured me that, if I cancelled, I could get the approved vaccine in February instead, if I wanted it. I phoned a good friend in Baltimore who’s a research scientist. She said, this is a new virus, we know it mutates, you’re 75, don’t take a risk that’s not been researched.

So I won’t. I cancelled the appointment to have a vaccine – the appointment I’ve been dreaming about getting for weeks. I feel as though I’ve cut off my right arm.

• Francis Beckett is a journalist, author and playwright whose books include Clem Attlee: Labour’s Great Reformer (Haus Publishing).