
A third dose can be added after 28 days for immunocompromised people in some countries.

There is no evidence that a third booster dose is needed to prevent severe disease in healthy adults. Therefore, to avoid deaths where supplies are limited, the WHO recommends delaying the second dose by up to 12 weeks to achieve high coverage of the first dose in high-priority groups. Data show that first dose efficacy persists for up to ten weeks. The World Health Organization (WHO) recommends an interval of 28 days between doses. The initial course consists of two doses. The vaccine is given by intramuscular injection into the deltoid muscle on the shoulder.


The Moderna COVID‑19 vaccine is used to provide protection against infection by the SARS-CoV-2 virus in order to prevent COVID‑19. 6.3.2 Heterologous prime-boost vaccination.6.3.1 Homologous prime-boost vaccination.This vaccine candidate can potentially be kept in refrigerators instead of freezers, making distributions easier especially in developing countries. On 15 March 2021, Moderna's second COVID‑19 vaccine ( mRNA-1283) started phase I clinical trials. It is authorized for use at some level in many countries.

It is an RNA vaccine composed of nucleoside-modified mRNA (modRNA) encoding a spike protein of SARS-CoV-2, which is encapsulated in lipid nanoparticles. It is designed to be administered as two or three 0.5 mL doses given by intramuscular injection at an interval of at least 28 days apart. It is authorized for use in people aged twelve years and older in some jurisdictions and for people eighteen years and older in other jurisdictions to provide protection against COVID-19 which is caused by infection by the SARS-CoV-2 virus. The Moderna COVID‑19 vaccine ( INN: elasomeran ), codenamed mRNA-1273 and sold under the brand name Spikevax, is a COVID-19 vaccine developed by American company Moderna, the United States National Institute of Allergy and Infectious Diseases (NIAID) and the Biomedical Advanced Research and Development Authority (BARDA).
