People under 60-years old who have had a first shot of AstraZeneca’s COVID-19 vaccine should receive a different product for their second dose, recommended Germany’s vaccine commission, known as STIKO.

Earlier in the week, Germany said only people aged 60 and over should be administered the AstraZeneca vaccine due to the rare but severe occurrence of thromboembolic side effects. It said it would make a separate recommendation later on younger people who had already received a first shot, Reuters reports.

In an updated recommendation on its website, STIKO said there was no scientific evidence on the safety of a mixed series of vaccines.

Until the appropriate data is available, STIKO recommends for people under 60 years old that instead of the second AstraZeneca dose, a dose of an mRNA-vaccine should be given 12 weeks after the first vaccine,” STIKO said.

Messenger RNA (mRNA) vaccinations include those made by Pfizer-BioNTech and Moderna.

Read STIKO recommendations HERE