WASHINGTON: Fake doses of the Pfizer coronavirus vaccine were being sold in Mexico and Poland for as much as $2,500 a shot, the US drugmaker and an official confirmed.

At a clinic in Mexico some 80 people received bogus vaccines, which appeared to have been physically harmless though offered no protection against the potentially deadly disease ravaging the country, a report in the Wall Street Journal said.

Mexico's government spokesman on Covid-19 Hugo Lopez-Gatell said "no product was found that could affect" the health of those scammed, adding several people had been arrested.

Lopez-Gatell said the false drugs were offered on social networks for up to $2,500 per unit and were detected by cyber police.

The vials were found in beer coolers and were initially identified by fabricated lot numbers and expiration dates, Mexican officials said.

Confiscated vials of bogus Covid vaccines in Poland contained a cosmetic substance, thought to be anti-wrinkle cream, the company said.

"We are cognizant that in this type of environment -- fueled by the ease and convenience of e-commerce and anonymity afforded by the internet -- there will be an increase in the prevalence of fraud, counterfeit and other illicit activity as it relates to vaccines and treatments for Covid-19," a Pfizer spokesperson told ABC News.

In February, health authorities in the northern Mexican state of Nuevo Leon warned about "clandestine" sales of "alleged Covid vaccines" and urged people not to take them.

In March, the World Health Organization also warned of "falsified" Pfizer vaccines found in Mexico and warned that the shots "may still be in circulation in the region."

Pfizer tested the bogus vials and found they did not contain the two-shot vaccine it developed with BioNTech.

Lev Kubiak, Pfizer's head of global security, said the desperate need and the shortfall in vaccines had led to the scams.

"We have a very limited supply, a supply that will increase as we ramp up and other companies enter the vaccine space. In the interim, there is a perfect opportunity for criminals," he told the Wall Street Journal.

Mexico is also examining a shipment of 6,000 doses of what is claimed to be the Russian vaccine Sputnik that were seized on a private plane headed for Honduras last month, the newspaper said.