The Covid-19 mink variant that led to a cull of all mink in Denmark and the resignation of the country’s agriculture minister on Wednesday, is “very likely extinct”, said Denmark’s health ministry. The cull was sparked by research from one of Denmark’s public health bodies, the Statens Serum Institut (SSI), which showed that a mink variant of the Sars-CoV-2 virus called C5 was harder for antibodies to neutralise and posed a potential threat to vaccine efficacy. A press release from the Danish Health Ministry on Thursday said the SSI had not found the C5 variant since September. It said: “the sequencing of the positive tests are showing we have not been able to find the mink variation with Cluster 5 since 15 September and because of this the SSI is estimating that this variant has very likely has died out.” Despite political backlash the cull has continued, and farmers have until midnight Thursday to cull all mink in the country. Scientists broadly welcomed the C5 extinction announcement. “This is good news, although I suspected Cluster 5 was extinct already,” said University College London (UCL) Genetics Institute director Francois Balloux. “Its prevalence was never that high and has not been observed since last September.” Balloux said, in his view, the “concerns over Cluster 5 may have been overestimated at the time”, but said this did not mean that the cull had been unnecessary. “No, the cull was not unjustified. Mainly because of the number of mink infected with Covid-19. The mutation was not really the justification for me. It was the large mink reservoir of Covid-19. I would also mention that minks escape regularly, so you don’t want that risk of infecting the wild animal population either.” He added that although C5 was just one of several mink mutations in circulation, it had been the most worrying because of its structure. “It had four mutations in the spike protein but only one in the receptor binding domain (RBD), the Y453F mutation. It is the RBD area that is the most important in terms of the risk of reducing vaccine efficacy.” Balloux’s UCL colleague, microbiologist Prof Joanne Santini, said this indicated the Danish had successfully contained its transmission, but sounded a note of caution. “I would be interested to know whether the claim of extinction was due to quarantining people infected, isolating their contacts as well culling the infected mink, or if C5 died out naturally.” It would be critical, as well, Santini said, to exclude the possibility of other animals being infected. “Time will tell,” she said. Nor does the C5 extinction rule out the risk of similar mutations, and much is still unknown, she said. Danish thinktank estimates put the cost of mink farm closures at about 3bn Danish kroner (£360m), and last week Denmark’s breeder association and the world’s largest fur auction house, Kopenhagen Fur, announced a “controlled shutdown” over the next three years. Sweden’s health agency said on Thursday that a number of Covid-19 cases had been confirmed in people who work in the mink industry. Authorities are analysing viruses from the infected people and infected minks to see if there is a link between the cases and their contact with minks, the agency said in a statement. Reuters contributed to this report