Pfizer says booster shot promising against Omicron

Health worker receives Pfizer booster shot in Quezon City, Philippines - November

Pfizer and BioNTech have said a booster jab of their coronavirus vaccine promises to be an effective defence against the new Omicron variant.

Three doses provide a similar level of antibodies against Omicron to that of two doses against other variants, the companies said after a small study.

The World Health Organization (WHO) earlier said vaccines should still work against severe Omicron cases. Researchers across the world are piecing together data about Omicron. It is the most heavily mutated version of coronavirus found so far.

In a statement on Wednesday, Pfizer chief executive Albert Bourla said protection against the variant would be improved with a third dose of the jab. “Ensuring as many people as possible are fully vaccinated with the first two dose series and a booster remains the best course of action to prevent the spread of Covid-19,” he said.

However, Pfizer and BioNTech noted that the results were preliminary and said they would continue to collect data and “evaluate real-world effectiveness”. They added that they were developing an Omicron-specific vaccine which would be ready for delivery within 100 days, pending regulatory approval.

Both the Pfizer/BioNTech research and a new South African study – not yet peer-reviewed – found that the vaccine might result in far fewer neutralizing antibodies against Omicron than against the original Covid-19 strain. Pfizer/BioNTech, however, said a third dose boosted those antibodies by a factor of 25, making the level of protection comparable to that of two doses against other variants.

Multiple studies have now shown Omicron is better than other variants at evading part of the immune system. The studies have focused on neutralizing antibodies that stick to the virus and stop it infecting our body’s cells. If these are less effective then it could increase the chances of you catching Covid-19, but it is far too soon to quantify how likely that is to happen.

There are also signs that a third dose or a mix of past infection and vaccines would minimize the risk. The vaccines are still highly likely to protect most people against severe disease because they train far more of the immune system than just neutralizing antibodies.

T-cells, which kick in once an infection is under way, are better at dealing with variants as they can attack different parts of the virus. However, a large and sudden wave of Omicron could still cause problems even if it is mild for most people.

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