PUNE, India (Reuters) - The CEO of the world's biggest vaccine maker, Serum Institute of India, said the company has bolstered its manufacturing ahead of launches over the next few years of shots against diseases like malaria and dengue by repurposing facilities used to make COVID-19 immunizations.

With COVID manufacturing scaled back as demand ebbs, the company is using those facilities to instead manufacture its newer shots, which it estimates will boost total production by two and a half billion doses, CEO Adar Poonawalla said in an interview.

Serum produces AstraZeneca's ( AZN ) COVID-19 vaccine under the brand name Covishield in India, and also makes Novavax's ( NVAX ) protein-based COVID shots.

It invested $2 billion during the peak of the global health crisis to boost production.

The company currently sells about 1.5 billion total vaccine doses every year, and estimates a total production capacity of as much as 4 billion doses.

"And this is also important because if there is a pandemic again in the future, we can vaccinate the whole of India in a matter of three months, three to four months," Poonawalla said.

The company is in talks with other countries and governments to utilize those facilities in the event of future outbreaks, he said, but did not provide further details on the discussions.

Poonawalla said Serum has capacity to manufacture 100 million doses of its malaria vaccine, and could scale up further depending on demand. It has already produced 25 million doses ahead of a launch in the coming months.

The ancient mosquito-borne disease still kills more than half a million people, mainly young children in sub-Saharan Africa, every year.

Poonawalla said Serum would focus on exporting its vaccines, such as the malaria shot, to other countries, rather than sign technology transfer deals.

Serum is also testing a single-dose vaccine for dengue, another mosquito-borne, painful and sometimes fatal disease, which it developed building on research done by the U.S. National Institutes of Health.

That vaccine is in early- to mid-stage trials in India and the company expects to complete late-stage trials in the next three years, the CEO said.

Japan's Takeda Pharmaceutical also makes a dengue shot, which is available in countries like Indonesia and Thailand, as well as Argentina and Brazil, which is currently dealing with a major outbreak and not enough vaccine.

Other companies such as Indian Immunologicals are also developing vaccines against the disease.