Comparison of COVID-19 vaccination regimens

In a recent study published on medRxiv* preprint server, researchers evaluated severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) neutralizing antibodies in Chile.

Diminished protection from natural and vaccine-induced immunity against coronavirus disease 2019 (COVID-19) has exacerbated morbidity and mortality caused by the pandemic. This resulted in increased susceptibility to disease and public outbreaks.

About the study

In the current study, researchers compared different COVID-19 vaccination regimens in Chile based on levels of SARS-CoV-2 neutralizing antibodies (nAbs).

The team measured the neutralization ability in human serological samples using pseudotyped vesicular stomatitis virus (VSV) having a sequence encoded for enhanced green fluorescent protein (GFP) which served as a reporter gene forming VSV-GFP -Spike SARS-CoV-2 Strain Wuhan. The samples analyzed in the study were collected from people enrolled in a SARS-CoV-2 seroprevalence study.

A total of 2,198 serum samples were collected from individuals aged seven years and older in November 2021. Six separate cohorts of SARS-CoV-2 positive samples were formed based on reported history of natural infection using five vaccination regimens that were used most frequently, which included two CoronaVac (CC), two Pfizer (PP), CC followed by one Oxford AstraZeneca (CCO), CC followed by one Pfizer (CCP ) and three Pfizer vaccines (PPP). The team randomly selected 20 people from each of six groups.

The level of nAb response was assessed based on the inhibitory concentration in which 50% of viral entry was inhibited (IC50). This IC50 was estimated for each serum sample by estimating the observed GFP fluorescence which showed the amount of viral entry of the VSV-GFP-Spike SARS-CoV-2 pseudotype.

Results

The results of the study showed that 97.3% of the total serum samples analyzed were seropositive. About 82.5% of the samples exhibited an atn response while no significant differences were observed based on gender and age. Notably, nAb levels were significantly higher in non-smokers and in those who received their booster doses of the COVID-19 vaccine. nAb levels showed considerable variation depending on the vaccination regimen used.

The team also observed that with respect to nAb levels, the cohort displaying only a basal immunization pattern had comparable nAb levels to naturally infected patients. However, people who had received their COVID-19 booster vaccine showed significantly higher nAb levels than primary vaccinees and naturally infected people.

Furthermore, the team observed that administration of PPP showed the highest median nAb response, whereas no substantial distinction was found after administration of the CCP regimen. In addition, the atn response was significantly higher than that of CCO recipients. The team also found that all three booster vaccination regimens resulted in remarkably higher nAb levels than the naturally infected groups and the CC and PP-administered groups.

Among the basic vaccination regimens such as CC and PP administration, significantly higher levels of nAb were observed for the PP regimen than for the CC regimen. The team also found a decrease in antibody titers for the groups vaccinated with the basal regimens but not for the groups vaccinated by boost.

Overall, the study results showed that the COVID-19 booster vaccine dose significantly increased anti-SARS-CoV-2 nAb levels, regardless of vaccination regimen or induced nAb levels. by natural infection.

*Important Notice

medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be considered conclusive, guide clinical practice/health-related behaviors, or treated as established information.