Data Byte: comparing clinical data from five COVID-19 vaccines

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Five groups have reported early-stage COVID-19 vaccine data in humans and the findings suggest all of the vaccines may require two doses to induce high neutralizing antibodies and T cell responses, which could make it make it more challenging to meet manufacturing projections.


Figure: Clinical readouts

The good news is all five vaccines were able to induce neutralizing antibodies in study subjects, with titers and response rates generally correlating with the amount and number of doses.

CanSino Biologics Inc. (HKEX:6185) only tested a single dose of Ad5-nCoV, and the company reported the lowest neutralizing antibody titers of the group, about tenfold less than FDA’s recommendation of 160 for convalescent plasma. According to ClinicalTrials.gov, CanSino is evaluating single and double immunizations in a Phase I/II trial in Canada.

AZD1222 (ChAdOx1 nCoV-19) from AstraZeneca plc (LSE:AZN; NYSE:AZN) and the University of Oxford approached the 160 benchmark at its high dose, and Mene Pangalos, EVP of BioPharmaceuticals R&D at AZ, said on July 20 that the company is “veering towards a two high doses strategy” (see “Timelines for AZ/Oxford Vaccine”).

A single 60 µg dose of BNT162b1 from partners Pfizer Inc. (NYSE:PFE) and BioNTech SE (NASDAQ:BNTX) produced less neutralization activity than delivery of the lowest two-dose regimen (a pair of 1 µg doses) in a Phase I/II study, supporting use of two doses of that vaccine as well.

At their highest doses, BNT162b1 and mRNA-1273 from Moderna Inc. (NASDAQ:MRNA) produced the most neutralization activity across the five vaccines, though direct comparisons need to be taken with a grain of salt due to the different assays employed to measure the activity.

Sinovac Biotech Ltd. (NASDAQ:SVA) reported that a two-dose regimen of CoronaVac led to 90% neutralizing antibody response rate in a Phase II trial, though it disclosed little else about the study.

All of the vaccines also induced T cell responses in subjects, which could facilitate long-term protective immunity,

The ability to trigger a humoral and cellular immune response is important at this stage because it isn’t yet clear which will correlate with protection against infection.

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