One question rippled through the queue outside a makeshift inoculation centre in Rio de Janeiro's beachside neighborhood of Copacabana on a recent morning: "Which vaccine are they using?"
Despite the world's second-highest death toll and infections running high, people across Brazil are refusing to receive their shot if the vaccine being used is not to their satisfaction.
Local media have dubbed them "the vaccine sommeliers".
There are no official figures on the total number of people cherry-picking their vaccines, but dozens of towns in Brazil have sought to crack down on the practice, taking the names of those who refuse to be inoculated with the shot on offer and moving them to the back of the queue.
Public health experts in Brazil say the practice and the misinformation — or poorly understood information — that fuels it, is threatening to undermine the country's vaccination campaign.
'Selfish'
It is also, they say, very selfish.
"The person is putting themselves at risk and ends up putting the entire system in danger," said Alexandre Naime Barbosa, an infectious diseases professor at São Paulo State University. "It shows a lack of empathy, an enormous selfishness."
The trend comes as many countries have already vaccinated most of their populations and are lifting restrictions.
The Brazilian Society of Immunisations said most incidents involve people refusing vaccines from China's Sinovac or — to a lesser extent — Astrazeneca. Instead they seek out shots from Pfizer and Johnson & Johnson.
WhatsApp groups have popped up with people swapping tips on which vaccination centres are offering the more sought-after shots.
Some are worried Sinovac's CoronaVac does not work as well, while others fear Europe and the US might not recognise it as travel restrictions are lifted for the fully vaccinated.
Dispel concerns
Brazilian health experts are rushing to dispel concerns, particularly about CoronaVac, fighting a wave of criticism including from President Jair Bolsonaro who said of the Chinese vaccine's use earlier this month: "It didn't work out."
Late-stage trials in Brazil found CoronaVac to have a 50 per cent efficacy at preventing symptomatic infection, compared to 76 per cent for Astrazeneca and 95 per cent for Pfizer.
But in a real-world context, public health experts here argue, CoronaVac has shown itself to be very effective in reducing hospitalisation and death.
"When you look at what really matters, reducing the number of hospitalisations and deaths, all the vaccines we have in Brazil have a very high efficacy," Prof Barbosa said.
Choosing your vaccine is an ignorant gesture that lacks commitment to public health
In Serrana, a town in Sao Paulo state, where almost the entire adult population were vaccinated with CoronaVac as part of a study, deaths were reduced by 95 per cent. Hospitalizations fell 86 per cent and symptomatic infections by 80 per cent.
Public health experts have also stressed that the risk of developing blood clots as a result of taking the Astrazeneca vaccine are incredibly rare.
No vaccine, scientists stress, ever entirely removes the chance of death.
"Choosing your vaccine is an ignorant gesture that lacks commitment to public health," said Dimas Covas, the president of the Butantan Institute which is producing CoronaVac in Brazil.
