Pfizer's coronavirus shot shows promise by triggering immune response

Experimental coronavirus vaccine from Pfizer triggered levels of antibodies up to THREE TIMES greater than those seen in recovered patients, early data shows

  • Researchers randomly gave 45 healthy volunteers either a low dose, a medium dose or a high dose of a coronavirus vaccine, or a placebo
  • Those who received the vaccine were given two shots, except the high dose group after half developed fever
  • The vaccine generated levels of neutralizing antibodies between 1.8 and 2.8 times greater than those seen in recovered patients 
  • No life-threatening side effects were seen and Pfizer hopes to start a large-scale human trial later this summer 

An experimental coronavirus vaccine being tested by Pfizer Inc and its German partner BioNTech showed encouraging early results, the companies announced on Wednesday.

The trial recruited 45 people, who received either a low, medium or high dose of the vaccine in two shots or a placebo.    

Volunteers given either the low or medium dose had immune responses in the range expected to be protective, when compared to COVID-19 survivors, according to the preliminary findings.

The results, which were published on pre-print site medRxiv.org, have been submitted for publication in a scientific journal, but have not yet been peer-reviewed.    

Researchers randomly gave 45 healthy volunteers either a low dose, a medium dose or a high dose of a coronavirus vaccine, or a placebo. Pictured: The first patient enrolled in Pfizer’s COVID-19 vaccine clinical trial at the University of Maryland School of Medicine in Baltimore receives an injection, May 4

Those who received either two shots of the low or medium dose of the vaccine generated levels of neutralizing antibodies between 1.8 and 2.8 times greater than those seen in recovered patients (above)

‘We still have a ways to go and we’re testing other candidates as well,’ Philip Dormitzer, chief scientific officer for viral vaccines at Pfizer’s research laboratories, told STAT News. 

‘However, what we can say at this point is there is a viable candidate based on immunogenicity and early tolerability safety data.’ 

The vaccine candidate from Pfizer and Biotech uses part of the pathogen’s genetic code to get the body to recognize the coronavirus and attack it if a person becomes infected. 

For the study, three groups of 12 received either a 10-microgram dose, a 30-microgram dose or a 100-microgram dose. Nine were given a placebo.

The highest dose shot caused fevers in about half of the group, so a second shot wasn’t given.

Three weeks later, participants were given a second dose. Following that, 8.3 percent of the 10-microgram group and 75 percent of the 30-microgram reported fevers.  

However, these side effects did not result in hospitalization, nor were considered life-threatening, and resolved after about one day.  

The immunization generated not just antibodies against the virus but specifically neutralizing antibodies, meaning they stop the virus from infecting human cells.

Results showed the levels of neutralizing antibodies were between 1.8 and 2.8 times greater than those seen in recovered patients. 

Volunteers who received one 100-microgram dose had lower levels of antibodies than those who were given two shots of the low or medium dose. 

Following news of the preliminary results, shares of Pfizer rose by four percent on Wednesday.

The US pharmaceutical giant hopes to begin a large-scale trial this summer, but did not specify which jab it would be testing. 

Around 200 vaccines are being developed around  the world with more than 15 currently in later-stage human trials such as AztraZeneca in partnership with Oxford University, Inovio and Moderna.

A number of pharmaceutical companies are expected to begin human trials later this summer including Johnson & Johnson, Merck and Sanofi.  

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