“These are the best preliminary results I'm aware of for a vaccine of this type,” European Union (EU) vaccine expert Manuel Romaris told the Dagens Nyheter (DN) newspaper.
“It's extremely interesting. The Swedish researchers seem to be on the right track.”
The new Phase II study, which analyzed the vaccine's effects on people's immune systems, is to be presented at an AIDS vaccine conference in Paris on Monday.
The healthy test subjects in Tanzania who received Hivis developed specific immune cells which destroy HIV-infected cells in the body, as well as anti-bodies to fight the HIV virus strain included in the vaccine.
“It's really an unexpected result. The vaccine is safe and it creates an immune defence,” professor Britta Wahren, a virologist at Karolinska Institutet, and one of the researchers behind the study, told the newspaper.
The results indicate the Swedish vaccine may even provide better protection than a promising Thai vaccine unveiled on September 24th.
"We hope that our vaccine could increase protection to 50 percent," Wahren told AFP.
The vaccine in Thailand tested by Thai and US researchers cuts the risk of HIV infection by a third, an achievement described by the World Health Organisation (WHO) as a "significant scientific advance."
"Our vaccine includes more strains of the virus -- from Europe, Africa, the US and Asia -- and therefore provides a broader protection," Wahren said.
The Swedish vaccine was tested on 60 healthy policemen in Tanzania in what is called a Phase II study, an interim phase between when a vaccine is tested on a very small group of volunteers to assess its safety, and a Phase III trial, a large-scale investigation among thousands of people that focuses especially on effectiveness.
The researchers looked at whether the vaccine was safe to use and how the body's immune system reacted to it.
The results were so encouraging that the researchers are keen to carry Phase III testing, Wahren said.
"We don't have the financing to do that yet. But we hope that we will get it after presenting our results," Wahren said.
Despite the promising results, it remains too early to say whether or not Hivis can serve as an effective defence against HIV.
The Phase II study, which has yet to be published in a scientific journal, was carried out in cooperation with researchers in the United States and Tanzania and cost around 35 million kronor ($5 million).
The Swedish International Development Cooperation Agency (Sida) contributed 9 million kronor, while the European Union provided the remainder of the funding, according to DN.