Reinforcement against COVID would protect more after six months

They are administering the booster doses in much of the world to boost protection against COVID-19, raising questions about when exactly they should be given. While there are no clear answers, doctors say there is a downside to applying them too early.

The immune system takes time to develop its defenses. After vaccination or a natural infection, the lymph node cells begin to mature to be better prepared if they encounter the pathogen again. It takes several months to build what is known as immune memory.

A booster dose given several months after the immune system has been activated by an initial series, usually two doses, can strengthen your response, he said. Stanley Plotkin, veteran vaccinologist and emeritus professor of pediatrics at the University of Pennsylvania in Philadelphia.

The additional inoculation triggers a surge of antibodies that are more adept at preventing a range of SARS-CoV-2 variants, he said.

“That interval could be as short as four months, but generally speaking, a six-month interval is probably best.“, said Plotkin, whose pioneering research led to a rubella vaccine more than 50 years ago.

An even shorter interval, such as two months, could compromise the body’s ability to establish a lasting immune response, he said in an interview.

That’s because the immune system takes time to rejuvenate itself after rapidly and crudely producing antibodies against a new enemy, said John Wherry, director of the institute for immunology at the university’s Perelman School of Medicine. As the “emergency response”, The body works to produce better antibodies that can be amplified quickly when stimulated with another dose of the vaccine or by a natural infection.

The so-called neutralizing antibodies that adhere to coronavirus particles and prevent them from entering healthy cells are essential to defend against COVID-19. They decrease months after vaccination or a natural infection; however, they increase the risk of a SARS-CoV-2 infection. That prompted some health authorities to recommend an additional dose for adults to increase their protection against a new wave of COVID fueled by the hyper-infectious delta variant.

A third dose of the vaccine from Pfizer Inc. or Moderna Inc. about eight months after the second dose led to a 25-fold increase in antibody levels, according to a study from Chicago Northwestern University in 33 healthy adult volunteers.

There is evidence to suggest that even wider ranges may be helpful, he said. Miles Davenport, head of the infection testing program at the Kirby Institute at the University of New South Wales in Sydney. With the vaccine AstraZeneca Plc, the peak of the immune response can come if a booster is given at least a year after the second dose, he said.

“What we don’t know at this point is how long the response will be after that third dose.“, said Plotkin. Booster doses may need to be given periodically, especially to older people, to prevent COVID epidemics, he said.

Annual doses probably won’t be necessary for most people in the long term, he said. Davenport. “We will have our annual booster dose with exposure to circulating virus“, said.