Some conditions laid down in the government's abandoned tender for swine flu vaccine were too difficult to meet, a big drug maker said yesterday. The comment from Swiss drug firm Novartis came a day after the government announced it had cancelled its tender for five million doses of vaccine - raising concerns about whether it can secure supplies before the winter flu peak. Novartis, one of the five main makers of flu vaccines, said a big obstacle was a requirement that the supplier say when it could obtain approval for the drug and when it would be delivered. That was because no company had yet produced a vaccine, said Novartis Hong Kong spokeswoman Wong Sui-chau said. 'We can only give a rough estimate,' she said. The government remained tight-lipped yesterday on why the tender was cancelled. Health officials have already begun talks with the mainland about it supplying a vaccine. Basel-based Novartis started clinical trials of a swine flu vaccine on people in the United States and Europe on August 6. The trials are expected to be finished in October. Ms Wong would not say whether her company had put in a bid, but said she thought any drug maker would find the tender conditions 'challenging and difficult'. Another 'really challenging' requirement was one for the manufacturers to take back unused vaccine. Another condition of the the tender was that Hong Kong be allowed to buy between three million and six million doses of vaccine. In Beijing, where he is attending an international swine flu conference, Secretary for Food and Health York Chow Yat-ngok said that usually if no single tender met requirements, the government could retender or mount a restricted tendering exercise. 'This is what we are considering,' he said. Health Minister Chen Zhu said mainland manufacturers would be approved to produce the first batch of vaccine in three weeks, as clinical tests had yielded good results. He said Beijing would try to help Hong Kong and Taiwan with supplies. The Hong Kong government has estimated that the inoculation of two million at-risk people, including the very young, elderly and chronically ill, will take five to six months. A medical professional familiar with the tender process said mainland vaccine production lines involving international drug makers could be a possible source of supplies to Hong Kong. Medical legislator Leung Ka-lau said the government owed the public an explanation as to why the tender failed. 'The government cannot just say everything is confidential.' Chinese University pharmacy school director Vincent Lee said only five drug makers in the world could make the vaccine and they could meet just a third of demand. 'I do not know a lot about the mainland manufacturers but we need to be a bit cautious. Experts should inspect the vaccine when we get it.' Hong Kong confirmed 326 new swine flu cases yesterday, taking the total to 8,535.