Update on COVID-19 Variants and Vaccines

Volume 16, Issue 3

Nothing is static in the world of COVID-19, as new subvariants continue to spin off the original Omicron (B.1.1.529) variant.

By now, most of you have likely heard of the BA.2 subvariant of Omicron, as this has been circulating in the United States for some time. Unfortunately, new subvariants continue to emerge, and BA.2.12.1—which has 2 more mutations (L452Q and S704L) than BA.2—as well as BA.4 and BA.5 have appeared.

In this week’s issue of Talking Therapeutics, we’ll look at 2 new papers published in the New England Journal of Medicine which tackle immune escape with the new subvariants and the ability of vaccination vs prior infection to protect against Omicron infection.

Point 1: Some Immune Escape With New Subvariants

A new paper published this week examined the neutralizing antibody titers against several common variants and subvariants in both vaccinated patients and those who survived natural infection with the Delta and Omicron variants.

The key takeaways of the paper are:

• Boosters sufficiently protected against the BA.4/5 and BA.2.12.1 subvariants, but authors noted neutralizing-antibody titers were lower against these strains as compared to BA.1 and BA.2. Patients with only 2 vaccine doses had lower neutralizing-antibody titers across the board regardless of the virus strain.
• Patients admitted to the ICU during the Delta wave had predominant neutralizing-antibody titers against the Delta variant. However, protection against Omicron infection was noted, and “BA.4/5 and BA.2.12.1 had less escape from neutralization in serum samples obtained during the Delta wave.”
• Patients admitted to hospital (but not ICU) with Omicron had neutralizing-antibody titers against BA.4/5 and BA.2.12.1 that were lower than those against BA.2.

“Overall, these results showed that infection during the BA.1 wave did not appear to offer effective protection against the newly emerged sublineages,” study authors said.

Point 2: Vaccination Plus Prior Infection Superior for Preventing Reinfection

In another paper out this week, the authors sought to compare the relative effectiveness of immunization vs prior infection in preventing new infection with the Omicron subvariants BA.1 and BA.2.

These authors found previous infection alone was 46.1% effective against symptomatic BA.2 infection (95% CI, 39.5-51.9).

In participants with no previous infection, the effectiveness of immunization with 2 vaccine doses was negligible (-1.1%; 95% CI, -7.1-4.6), while the effectiveness of 3 doses was 52.2% (95% CI, 48.1-55.9). In people with previous infections, 2 vaccine doses were 55.1% effective (95% CI, 50.9-58.9), and the effectiveness of 3 doses was 77.3% (95% CI, 72.4-81.4).

Authors reported similar findings for protection against BA.1 infection. There were no significant differences between Pfizer-BioNTech and Moderna vaccines.

“Vaccination enhanced protection among persons who had had a previous infection. Hybrid immunity resulting from previous infection and recent booster vaccination conferred the strongest protection,” authors concluded.