Separate Skelly et al. entry into separate descriptions about one thing each

[miseminger]

In S_convalescent_plasma_escape.txt.

# In over 90% of two dose mRNA vaccinees, heterotypic neutralizing titres (NT50) against B.1.1.7 and B.1.351 remain comfortably 
# above the level associated with immune protection in recent vaccine trials. However, in over 50% of convalescent COVID-19 
# individuals (5/9) and recipients of a only a single dose of mRNA vaccine (10/11) – heterotypic neutralization dropped to negligible levels, 
# particularly against B.1.351.
# Skelly et al. (2021) https://doi.org/10.21203/rs.3.rs-226857/v1 [Preprint (other)]
L18F;D80A;D215G;L242del;A243del;K417N;E484K;N501Y;D614G;A701V