I can't get vaccinated because of an immigration loophole. I feel invisible - and constantly worry about falling seriously unwell or infecting others.

• British nationals in Portugal like Mairead Finlay had to change residency paperwork after Brexit.
• She has been unable to get vaccinated because she still hasn't been issued with a new permit.
• "As people embrace their new freedom, I feel invisible, stuck in an endless merry-go-round."

I've been turned away from getting a COVID vaccine three times because of a paperwork issue.

After Brexit took effect at the end of 2020, British citizens in Portugal like me had to get new paperwork to obtain a health number here - a condition of getting the vaccine.

I can't get a health number unless I have a valid residency document. EU citizens can get one at the local council, but when Brexit happened, Brits had to upload existing EU documentation or apply via the Brexit portal - the new way to apply for residency.

Then, a permit would be issued following an appointment with the immigration department. According to the portal, these appointments were originally going to be available from January 2021.

Months later, I'm still waiting for one. The British Embassy said earlier this month the immigration department was still finalizing the process. It has been experiencing a backlog after it closed down altogether from February to April due to COVID restrictions.

Meanwhile, 87% of Portuguese adults are vaccinated - the second most vaccinated country in the world after the UAE.

This waiting game has made getting vaccinated difficult, time-consuming and frustrating.

The British Embassy said I could get a temporary health number to get vaccinated by going to a health center and showing my temporary digital residency certificate for UK nationals.

I went to three health centers in Madeira and none recognized this digital version, which didn't show my Portugal address. Staff at two claimed they had not even heard about temporary health numbers. I was turned away every time. At one, I had waited two hours. I had travelled nearly 15 miles from my home to reach another.

The third center told me I needed to show proof of a scheduled appointment with the immigration department before a health number could be issued. But I've been waiting nine months to get one with no date in sight. Calls and emails to the immigration department end in the same blanket response that I will be notified of an appointment in due course.

I also tried to schedule an appointment at a health center online, which was meant to be possible without having a health number.

I was signed up and ready when my age range was called in July. But I didn't receive the text I was meant to providing the location, date and time of an appointment. I registered twice more with no response. I rang many times and got different advice each time. Some advised to keep signing up online, others said to go to a local health center and try to sign up in-person.

I tried for the fourth time in August, and a month later received a text to say I had been invited to an open-house vaccination center, and could choose the day and the location with no appointment. It seemed like a long-awaited breakthrough, but it wasn't.

The text linked to a form that I needed to fill to get a password which would be shown on arrival. It required your health number.

This problem is so persistent that the British Embassy appealed for people to tell them where they were being turned away from and why.

It's been draining and stressful to continually chase a vaccine. At times I feel jealous of friends' and family's seamless experiences. For me, it's been nothing short of a battle, and one that's made even more irksome when I'm a tax-paying resident.

As people are embracing their newfound freedom, I feel invisible, stuck in an endless merry-go-round. There's a constant, underlying worry as restrictions loosen about becoming seriously unwell or infecting others.

It's inconvenient too. In mainland Portugal, being unvaccinated means I need to do a COVID test anytime I go to a restaurant or bar from Friday to Sunday, as well as to the gym, attractions or events.

Travel to a number of destinations is also off-the-cards thanks to the need for compulsory quarantining on top of any tests.

I haven't given up. I know others in the same situation who got their vaccination through persistently turning up to health centers. I'll keep trying. It's the only choice I really have.