However, the pharmaceuticals company says it has lessened the impact of its exposure in this area since the first quarter, and expects its second half results to further improve as it benefits from Relenza demand due to the global swine flu pandemic.
It also says new products, such as new vaccine ranges, should start to impact on sales.
Meanwhile, its consumer healthcare division, which includes brands such as Beechams and Nicorette, performed better, posting a 9% rise in sales in the quarter to £1.2bn.
A focus on growing consumer oral health brands such as mouthwash Corsodyl has delivered 4% growth in the sector in the UK, compared to the category which rose 1%.
Chief executive Andrew Witty says the group is working to increase its market share in emerging geographic markets such as China and Japan, which contributed 1.5% higher contributions to the group’s financial performance in the second quarter compared to the first.
Last month, GSK launched a daily mouthwash under the Sensodyne brand as part of a £8.7m cash injection to boost brand’s range and market share in the UK.
Sensodyne Pronamel mouthwash will be launched via a TV campaign in September as part of the healthcare multinational’s umbrella “experts” campaign. The advertising push is being handled by Grey.