Maria Ruiz admitted she was "afraid" but the 48-year-old nurse was determined to play her part in helping Cuba's ambitious drive to produce its own Covid-19 vaccine.
"It's not the same when I give it to a patient or when I receive it," she said, waiting for her shot of the Soberana 2 vaccine.
"Whenever it's good for me and for wider society, I'm there!"
Launched a week ago, the initiative aims to vaccinate 150,000 hospital workers, including technicians and maintenance staff, even before it has conducted clinical trials.
Cuba wants it to be the first vaccine made in Latin America to combat the deadly global virus.
The Russian Sputnik V vaccine was another to be administered widely before clinical trials were complete.
And unlike in traditional trials, this time "we're not using a placebo, it's the vaccine straight up," said Osiris Barberia Elejalde, a doctor and deputy director of epidemiology at the Heroes of Corinth hospital in the capital Havana.
The program has targeted hospital staff "because they are the ones in contact with the infected patients. That is to say, on the front line," she added.
- Gamble -
The search for a vaccine, begun in April 2020, quickly became a source of national pride in Cuba.
Hamstrung by more than half a century of US sanctions, Cuba has had to develop its own shots since the 1980s.
Faced with this pandemic, Cuba neither tried to buy vaccines from the world's leading manufacturers, nor benefit from the global Covax initiative to ensure jab access for poorer nations.
It may have seemed like a gamble but Cuba has four vaccines currently at various stages of clinical trials, including two in the final phase three: Soberana 2 and Abdala.
If either receives final authorization, it will be the first Covid vaccine developed and produced in Latin America.
Cuba is hoping to roll out its vaccination campaign in June, but will rely on intervention studies before then to start immunizing its population of 11.2 million.
Almost all 2.1 million residents of the capital Havana are due to receive their vaccine by May with six million people vaccinated by early August.
"Can you believe it, that in such a short space of time, a country under embargo, with so many needs, has made a quality vaccine," said Barberia, who insisted that while the intervention study is voluntary, so far "everyone" wants to take part.
Some "even want to bring their families but we said no!"
- Friendly countries -
In the Heroes of Corinth clinic, doctors, nurses and even pest controllers rub shoulders during the different vaccination stages: temperature checks at the entrance, blood pressure test and questionnaire on the first floor.
Following the jab, everyone must wait an hour before leaving in case of an adverse reaction.
Alejandro Larrinaga, a 64-year-old doctor wearing a mask, arrived just after 9:00 am.
He took part in medical missions in the past to Mozambique, Angola and South Africa.
This time he has a different mission.
"I was happy to come and get vaccinated, to boost my immune system," he said.
But, he added, "self-protection is more important than the vaccine."
It can take three weeks for a vaccine to take full effect.
Cuba, though, has been relatively unscathed by the pandemic, with almost 69,000 cases and 405 deaths.
Authorities want to complete their vaccination program this year and then offer the jabs to friendly countries.
In March, 100,000 doses of Soberana 2 were sent to Iran for testing, and 30,000 doses of Soberana 2 and Abdala will be sent to Venezuela in April.