Clusters of SARS-CoV-2 Lineage B.1.1.7 Infection After Vaccination With Adenovirus-Vectored and Inactivated Vaccines: A Cohort Study

Abstract

Background: Some studies have determined that the SARS-CoV-2 B.1.1.7 variant of concern (VOC) has been associated with increased transmissibility, hospitalization, and mortality. This study aimed to explore the factors associated with B.1.1.7 VOC infection in the context of vaccination with adenovirus-vectored and inactivated vaccines.

Methods: We analyzed epidemiological, clinical, and laboratory data from simultaneous COVID-19 outbreaks in a convent (Outbreak A) and in a long-term care facility (Outbreak B) in individuals vaccinated with a single dose of ChAdOx1 or two doses of the CoronaVac vaccine, respectively. First, we identified the viral lineages associated with these outbreaks by genome sequencing. Then, we assessed the relationship of viral load, specific immunoglobulin antibody levels, neutralization antibodies, case characteristics (age, vaccine type, and presence or absence of symptoms), and associations with risk of developing COVID-19.

Findings: On March 2021, we detected SARS-CoV-2 RNA in nasopharyngeal samples from 14 of 22 of the ChAdOx1 vaccine recipients (Outbreak A, n=26), and 22 of 42 of the CoronaVac-vaccinated individuals (Outbreak B, n=52) for breakthrough infection rates for ChAdOx1 of 63·6% and 52·4% for CoronaVac. Vaccinated individuals from Outbreak A received a single dose at least 23 days before the outbreak, and the Outbreak B was involved virus detection 5 to 27 days after a second dose. In these outbreaks, the median ages were 73 and 77 years old, respectively. The median viral loads were 3·4×10¹ and 2·3×10³ RNA copies per mL in Outbreaks A and B, respectively. In total for both outbreaks, 12 people had mild-COVID-19 while 26 were asymptomatic, but one case involving a person from Outbreak B was fatal. Based on analysis of SARS-CoV-2 genome sequences, we determined that outbreaks A and B were caused by two independent clusters of the B.1.1.7 VOC. Interestingly, the serum of PCR-positive symptomatic SARS-CoV-2-infected individuals had ~1·8 to 3·4-fold more neutralizing capacity against B.1.1.7 compared to the serum of asymptomatic, SARS-CoV-2-infected individuals, indicating that the levels of neutralizing antibodies induced by ChAdOx1 and CoronaVac were not correlated with protection against symptomatic infection.

Interpretation: These data suggest that the B.1.1.7 variant can escape from the immune response elicited by immunization with a single dose of an adenovirus-vectored vaccine or two doses of an inactivated vaccine. However, partial immunization with ChAdOx1 and the complete series of CoronaVac seemed to provide protection against severe COVID-19 and death in the large majority of individuals. Continued and rapid immunization combined with nonpharmaceutical interventions (e.g., masking and physical distancing), are necessary to break the SARS-CoV-2 transmission until herd immunity improves.

Funding Information: São Paulo Research Foundation, Brazilian Ministry of Science, Technology and Innovation and Funding Authority for Studies, Coordination for the Improvement of Higher Education Personnel, Wellcome Trust, Medical Research Council, National Institutes of Health, and Brazilian National Council for Scientific and Technological Development.

Declaration of Interests: All other authors declare no competing interests.

Ethics Approval Statement: All procedures followed the ethical standards of the responsible committee on human experimentation and were approved by the ethics committees from the University of Campinas, Brazil (Approval number: CAEE 31170720.3.0000.5404).