US pharmaceutical firm Moderna (MRNA) will deliver fewer than expected COVID vaccines to the UK, Canada and other countries following a shortfall in production in its European supply chain.
The drugmaker said that shipments to the European Union and Switzerland are on track.
But, added that it will make "adjustments" to expected second quarter delivery supplies in affected nations.
As a result, the Boston-based company will reduce the number of doses it is sending to the UK from this month, which will impact the inoculation targets in Q2.
Moderna produces vaccines for non-US markets in a plant in Switzerland, which is run by contract manufacturer Lonza. It fills vials for Great Britain and EU countries in Spain.
It comes after the UK announced on Friday that pregnant women in the country should be offered the Moderna and Pfizer (PFE) COVID vaccines, where available instead of the Oxford/AstraZeneca (AZN.L) one.
New advice from the government's Joint Commission on Vaccination and Immunisation (JCVI) said pregnant women are eligible for the coronavirus vaccine, and should be offered a jab at the same time as the rest of the population.
Assessments should be made based on their age and any clinical risks, the JCVI said.
The Moderna jab, which works in a similar way to the Pfizer vaccine, uses synthetic messenger RNA (mRNA) technology that can be quickly tweaked to address new mutations of a virus.
Scientists have suggested the changes could be made in as little as six weeks.
It is given in two shots, one month apart.
Britain has ordered 17 million doses of the Moderna vaccine, which has a 94% efficacy rate in trials.
It also ordered 100 million doses of AstraZeneca and 40 million doses of the vaccine by US drugmaker Pfizer and German biotech firm BioNTech.
In November, the UK became the first Western country to approve a coronavirus vaccine.
So far over 32.5 million people in the UK have received a first dose of the COVID vaccine, according to official data. Nearly nine million people have gotten their second jab.
WATCH: COVID-19: Pregnant women in UK should be offered vaccine, new advice says