Virus neutralizing antibody responses after two doses of BBIBP-CorV (Sinopharm, Beijing CNBG) vaccine
Authors: Ferenci Tamás , Sarkadi Balázs 
Published: July 2021

Background

Limited information is available on the effectiveness of the BBIBP-CorV (Sinopharm, Beijing CNBG) vaccine, especially in the elderly, despite the fact that it is approved in more than 50 countries.

Methods

Virus neutralizing antibody titres, as a rapidly available but highly predictive surrogate marker, were measured after two doses of the BBIBP-CorV vaccine in 450 subjects. Results were analyzed in a multivariable model accounting for age, sex and time since the administration of the second dose of the vaccine.

Findings

Sex and time since the second dose had little association with the antibody titres. Age, however, was highly relevant: measurable antibody levels were present in about 90% of individuals below the age of 50, but antibody production after BBIBP-CorV vaccination was strongly reduced with increasing age. A large number of elderly subjects, reaching 25% at 60 years, and up to 50% at ages over 80, were found not to produce any protective antibody.

Interpretation

Neutralizing antibody titre, as a correlate of protection for COVID-19 disease susceptibility, should help to evaluate the effectiveness of the BBIBP-CorV vaccine. Results suggest that proper measures should be undertaken to prevent a potential outbreak of COVID-19 in BBIBP-CorV vaccinated but eventually unprotected elderly individuals.

Funding

No specific funding was used to carry out the study.

Research in context

Evidence before this study

The BBIBP-CorV (Sinopharm, Beijing CNBG) vaccine was found to be effective, but the Phase 3 trial included few women, almost no elderly subject and no subject with preexisting medical condition. It is therefore especially important to monitor the real-world effectiveness of this vaccine, however when searching Pubmed for (Sinopharm OR BBIBP-CorV) AND vaccine AND (effectiveness OR efficacy OR antibody OR titre) in text words with no language or date restriction and with translation of the terms enabled, we found no such published study. The most rapid way to generate such evidence is the assessment of antibody response which was found to be highly predictive for disease susceptibility. This is of crucial importance as the vaccine is approved in more than 50 countries, and hundreds of millions have already been vaccinated with many planned to be vaccinated in the near future with this vaccine.

Added value of this study

Virus neutralizing antibody titres were measured after two doses of the BBIBP-CorV vaccine in 450 subjects. Results were analyzed in a multivariable model accounting for age, sex and time since the administration of the second dose of the vaccine. We found that sex and time since the second dose had little association with the antibody titres. Age, however, was highly relevant: while the vast majority of those below 50 years had measurable antibody levels, this rate quickly dropped with increasing age. In subjects aged 60 years, quarter, in those above 80 almost half had no detectable neutralizing antibody.

Implications of all the available evidence

The real-world effectiveness of the BBIBP-CorV vaccine should be carefully monitored. Elderly subjects are especially prone to produce no protective antibody after vaccination. This should be monitored, and proper measures should be undertaken to prevent a potential outbreak of COVID-19 in BBIBP-CorV vaccinated but eventually unprotected elderly individuals.