Kenya will pay about Sh200 per dose of the coronavirus vaccine and donors the balance of Sh100.
Each dose costs a maximum Sh300 and experts say two doses are likely to be required.
The cost-sharing decision was announced by Gavi, the Geneva-based Global Alliance for Vaccines and Immunisation. It is leading a programme to secure Covid-19 vaccines for developing countries.
Gavi said cost-sharing would promote country ownership of the vaccine access programme and motivate support from new donors such as development banks.
Kenya will also benefit from a Sh15 billion donation, shared among 92 developing countries, to help with the distribution.
"The allocation of this amount, [is] committed from Gavi'a core resources and intended to help these countries prepare for the delivery of Covid-19 vaccines," Gavi said in a statement.
At least nine vaccine candidates, if successfully registered, will be supported through the access programme called the Covid-19 Vaccines Advance Market Commitment (Covax AMC).
“The decisions today serve twin goals of moving forward rapidly with our need to ensure equitable access to Covid-19 vaccines via the Covax Facility and Covax AMC.
"They also support lower-income countries’ ability to maintain routine immunisation programmes and protect against the threat of other infectious diseases,” Gavi board chairman Ngozi Okonjo-Iweala said.
The ceiling $3 (Sh300) per dose is already heavily subsidised by earlier $150 million funding from the Bill and Melinda Gates Foundation.
Gavi has already sealed agreements with different vaccine manufacturers to secure 200 million doses for all countries participating in the access programme.
They comprise 76 self-financing economies that are also supporting another 92 developing nations.
The Gavi board also decided how much the supported nations would pay.
"The board also approved the policy that AMC-eligible economies would share the costs of Covid-19 vaccines and delivery, up to US$ 1.60 (about Sh160) – US$2 (Sh200) per dose – a mirror of the amount paid upfront by self-financing participants," Gavi said in a statement.
Countries would need to buy millions of doses because several studies have placed the preferred herd immunity levels at 70 per cent, which means millions of people need to be vaccinated to stop transmission.
Shipping a coronavirus vaccine around the world will be the largest transport challenge ever, according to the airline industry.
Gavi said some countries may not be able to afford the proposed cost-sharing and noted that flexibilities will be considered on a case-by-case basis until at least the end of 2021.
This is "to make certain that cost-sharing will not prevent or delay the introduction of Covid-19 vaccines in AMC-eligible economies and ensure these economies do not need to reallocate existing budgets, diverting resources from other vital routine vaccine programmes," Gavi said.
"The decisions will allow us to continue to collaborate with all countries and partners in this complex endeavour to ensure equitable access to Covid-19 vaccines and an end to the acute stage of the pandemic,” Gavi CEO Seth Berkley said on October 1.
Gavi finances almost 90 per cent of the cost of Kenya's childhood vaccines.
Covax, the vaccines pillar of the Access to Covid-19 Tools Accelerator, is co-led by Gavi, the Coalition for Epidemic Preparedness Innovations and the World Health Organisation.
(Edited by V. Graham)