CMAAO CORONA FACTS and MYTH 22nd April  One vaccine and one natural infection

Dr K K Aggarwal President CMAAO, HCFI, With input from Dr Monica Vasudev

India

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New Delhi, April 22, 2021 :

COVID Survivors May Need Only One Dose of Vaccine :

• People who have recovered from COVID-19 may only need a single dose of the Pfizer-BioNTech or Moderna vaccine to generate a sufficient antibody response, but COVID-naive individuals need two doses to achieve strong levels of immunity
• Researchers at the University of Pennsylvania examined antibody and antigen-specific memory B cells over time in 33 SARS-CoV-2-naive and 11 SARS-CoV-2-recovered adults who received the Pfizer-BioNTech or Moderna mRNA COVID-19 vaccine.
• Previous COVID-19 mRNA vaccine studies on vaccinated individuals have focused on antibodies more than memory B cells.
• SARS-CoV-2-naive individuals needed two vaccine doses for optimal increases in antibodies, particularly for neutralizing titers against the B.1.351 variant.
• Memory B cells specific for full-length spike protein and the spike receptor binding domain (RBD) were also efficiently primed by mRNA vaccination and detectable in all SARS-CoV-2-naive subjects after the second vaccine dose, though the memory B cell response declined slightly with age
• The study is reported in Science Immunology.
• In contrast, the SARS-CoV-2-recovered individuals mounted robust antibody and memory B cell responses after the first vaccine dose and there was no further increase in circulating antibodies, neutralizing titers, or antigen-specific memory B cells after the second dose.
• These data suggest that only a single vaccine dose in individuals confirmed to have previously been infected with SARS-CoV-2 may be enough to induce antibody and memory B cell responses
• Memory B cells a) are very efficiently primed by these mRNA vaccines
• These memory B cells (i.e. in COVID-recovered subjects) strongly correlate with new antibodies following vaccination.

SOURCE: https://bit.ly/3mZ7ljx Science Immunology, online April 15, 2021.

Chinese researchers are testing the mixing of COVID-19 vaccine doses developed by CanSino Biologics and a unit of Chongqing Zhifei Biological Products, according to clinical trial registration data.

A trial expected to involve 120 participants will test the safety and ability to trigger immune response of a dose of CanSinoBIO’s Ad5-nCoV treatment, followed by a dose of ZF2001 from Anhui Zhifei Longcom Biopharmaceutical at a 28-day or 56-day interval, according to clinical trial record site ClinicalTrials.gov, which is maintained by a department under the National Institute of Health of the United States.

Both vaccines are already being used in China’s mass vaccination drive.

CanSinoBIO said interim data from overseas Phase III clinical trials showed its Ad5-nCoV vaccine was 68.83% effective at preventing symptomatic COVID-19 disease two weeks after one injection, while efficacy four weeks after one shot fell to 65.28%.

Chinese researchers are also running trials on a two-dose Ad5-nCoV regimen, as well as an inhaled version of the vaccine.

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