AstraZeneca has been boosted by the news that US health regulators have given the green light to the firm's new four-strain flu vaccine.

The US Food and Drug Administration has approved FluMist Quadrivalent, manufactured by the Anglo-Swedish drugmaker's MedImmune unit. It is the first vaccine backed by the agency that contain four strains of the influenza virus, two strains each of influenza A and B.

Illness caused by influenza B affects children more than any other population, noted Karen Midthun, director of the FDA’s Center for Biologics Evaluation and Research. She added that “a vaccine containing the four virus strains most likely to spread and cause illness during the influenza season offers an additional option".

Bahija Jallal, MedImmune’s head of R&D, added that "the inclusion of an additional B strain in an annual influenza vaccine could provide a direct health benefit to individual vaccine recipients in the event that the correct B lineage either is not selected for inclusion in a trivalent vaccine, or if both lineages co-circulate".

Meantime, AstraZeneca is to appoint Leif Johansson, chairman of the Swedish mobile giant Ericsson and former chief executive of Volvo, as its new chairman.

Mr Johansson, who was also a non-executive director at Bristol-Myers Squibb from 1998 to September 2011, will be proposed for election at AstraZeneca's annual shareholder meeting on April 26. He will take over from September 1 when current chairman Louis Schweitzer retires.

Mr Schweitzer said Mr Johansson is "an outstanding businessman with a first-class track record leading multinational companies, as well as previous experience of the pharmaceutical industry".