Fighting Off Variants: Natural Vs. Vaccine-Induced Immunity

A non-peer-reviewed study's findings indicate that SARS-CoV-2 neutralizing antibodies (NAbs) titer elicited by the CoronaVac vaccine are much lower when compared to natural infection protection against the new coronavirus variants.

Since SARS-CoV-2 was confirmed in 2019, it has mutated many times, leading to the emergence of various virus variants referred to as variants of concern (VOCs).

Published on July 15, 2021, this study evaluated CoronaVac's effectiveness against the B.1.1.7 (Alpha), B.1.351 (Beta), and B.1.617.2 (Delta) strains in Thailand.

The researchers found that, despite equally robust production of S1-RBD-binding IgG and 100% seropositivity, sera from both CoronaVac vaccinees and naturally infected individuals had significantly reduced neutralizing capacity against all three variants.

While the NAb titers against Alpha and Beta were comparable, the Delta variant appears to be significantly more refractory to NAbs in all groups.

These results may help inform on CoronaVac NAb-inducing capacity, which is a proxy for vaccine efficacy. These results also have critical implications for public health decision-makers who may need to maintain efficient mitigation strategies amid a potentially high risk for re-infection, even in those people who have been previously infected.

CoronaVac is a 2-dose β-propiolactone-inactivated, aluminum hydroxide-adjuvanted COVID-19 vaccine administered on a 0/14-28-day schedule to prevent COVID-19 disease.

Note: Preliminary scientific reports are not peer-reviewed and should not be regarded as conclusive guide clinical practice or health-related behavior.