BETACORONAVIRUS mRNA VACCINES

1 . A betacoronavirus vaccine for a human subject, comprising a messenger ribonucleic acid (mRNA) formulated in a lipid nanoparticle,

wherein the mRNA comprises an open reading frame encoding a full-length betacoronavirus spike protein,

wherein the open reading frame comprises nucleosides consisting of N1-methylpseudouridine, adenosine, guanosine, and cytidine,

wherein the lipid nanoparticle comprises an ionizable cationic lipid, a neutral lipid, a cholesterol, and a polyethylene glycol (PEG)-modified lipid,

and wherein the vaccine is formulated for intramuscular injection to a human subject at a dose that comprises from 10-100 μg of the mRNA.

2 . The betacoronavirus vaccine of claim 1 , wherein the ionizable cationic lipid comprises a cationic lipid of Formula (I):

or a salt or isomer thereof, wherein:

R 1 is —R″M′R′ or C 5-20 alkenyl;

R 2 and R 3 are each independently C 1-14 alkyl or C 2-14 alkenyl;

R 4 is —(CH 2 ) n Q where Q is —OR, R is H, and n is 1, 2, 3, 4, or 5;

R 5 , R 6 , and R 7 are each H;

M and M′ are each independently —OC(O)— or C(O)O—;

R′ is C 1-18 alkyl;

R″ is C 3-14 alkyl; and

m is 5, 6, 7, 8, 9, 10, 11, 12, or 13.

3 . The betacoronavirus vaccine of claim 2 , wherein:

R 1 is —R″M′R′;

R 2 and R 3 are each independently C 1-14 alkyl;

R 4 is —(CH 2 ) n Q where Q is —OH, and n is 4;

R 5 , R 6 , and R 7 are each H;

M and M′ are each —OC(O)—;

R′ is C 1-18 alkyl;

R″ is C 3-14 alkyl; and

m is 6.

4 . The betacoronavirus vaccine of claim 2 , wherein the cationic lipid of Formula (I) or salt or isomer thereof comprises a cationic lipid of Formula (IA):

or a salt or isomer thereof, wherein:

l is 1, 2, 3, 4, or 5;

m is 5, 6, 7, 8, or 9;

M 1 is —OC(O)—;

M is —OC(O)—;

R′ is C 1-18 alkyl;

R 2 and R 3 are each independently C 1-14 alkyl; and

R 4 is —(CH 2 ) n Q where Q is —OH, and n is 1, 2, 3, 4, or 5.

5 . The betacoronavirus vaccine of claim 4 , wherein R 2 is C 6 alkyl and R 3 is C 8 alkyl.

6 . The betacoronavirus vaccine of claim 5 , wherein R′ is

7 . The betacoronavirus vaccine of claim 2 , wherein the cationic lipid of Formula (I) or salt or isomer thereof comprises a cationic lipid of Formula (IA):

or a salt or isomer thereof, wherein

l is 4;

m is 6;

M 1 is —OC(O)—;

M is —OC(O)—;

R 2 is C 1-14 alkyl;

R 3 is C 1-14 alkyl;

R 4 is —(CH 2 ) n Q, in which Q is —OH, and n is 4; and

R′ is C 1-18 alkyl.

8 . The betacoronavirus vaccine of claim 7 , wherein R 2 is C 6 alkyl and R 3 is C 8 alkyl.

9 . The betacoronavirus vaccine of claim 8 , wherein R′ is

10 . The betacoronavirus vaccine of claim 6 , wherein the dose comprises from 20-50 μg of the mRNA.

11 . The betacoronavirus vaccine of claim 10 , wherein at least 85% of the mRNA is encapsulated in the lipid nanoparticle as measured by a fluorescence assay.

12 . The betacoronavirus vaccine of claim 11 , wherein the lipid nanoparticle has a diameter of from 80-200 nm.

13 . The betacoronavirus vaccine of claim 12 , wherein the betacoronavirus vaccine comprises sucrose.

14 . The betacoronavirus vaccine of claim 2 , wherein the ionizable cationic lipid comprises