Health care workers who contracted COVID-19 and then got the vaccine had higher antibody levels


Health care workers who contracted COVID-19 and then got the vaccine had higher antibody levels than those who only got their shots, study finds

  • A new study compared vaccinated health care workers with and without a past case of COVID-19
  • Employees who had previously been infected had antibody levels 14% higher than those with a past confirmed infection one month after the second dose
  • After three months, levels were 19% higher and levels were 56% higher after six months
  • Researchers found that antibody levels were higher among health care workers who were exposed to Covid more than 90 days before their first vaccine dose 


Health care workers who contracted COVID-19 and then got the vaccine had higher antibody levels than those who only got their shots, a new study suggests.

Researchers compared medical employees who caught the virus before getting their first dose to those who had no history of previous infection.

They found that antibody levels generated in patients with a past case of Covid were up to 56 percent higher than those who had never contracted the virus.

What’s more, the team, from Johns Hopkins University School of Medicine, found that antibody levels were boosted even further if the worker had tested positive for COVID-19 more than 90 days before being vaccinated. 

A new study from Johns Hopkins University School of Medicine compared vaccinated health care workers with and without a past case of COVID-19. Pictured: Dentist Monique Iskarous (left) receives the Moderna COVID-19 vaccine from registered nurse Darlene Dickens-Jeffers, r in Anaheim, California, January 2021

A new study from Johns Hopkins University School of Medicine compared vaccinated health care workers with and without a past case of COVID-19. Pictured: Dentist Monique Iskarous (left) receives the Moderna COVID-19 vaccine from registered nurse Darlene Dickens-Jeffers, r in Anaheim, California, January 2021  

Employees who had previously been infected had antibody levels 14% higher than those with a past confirmed infection one month after the second dose. After three months, levels were 19% higher and levels were 56% higher after six months

Employees who had previously been infected had antibody levels 14% higher than those with a past confirmed infection one month after the second dose. After three months, levels were 19% higher and levels were 56% higher after six months

‘This finding adds to our understanding of how immunity against SARS-CoV-2 works, and builds upon an earlier study by our team that showed the mRNA vaccines yielded a robust antibody response, even if a person did not develop significant symptoms following vaccination or did not have a prior SARS-CoV-2 infection,’ said senior author Dr Aaron Milstone, a professor of pediatrics at Johns Hopkins, in a statement.

For the study, published in JAMA, the team looked at 1,960 Johns Hopkins Medicine health care workers.

All of them had received two doses of either the Pfizer-BioNTech or the Moderna COVID-19 vaccines.

Of the health care employees, 73 tested positive for COVID-19 before receiving their first vaccine dose. 

After adjusting for factor such as age and sex, the team compared antibody levels between the two groups. 

Researchers found that antibody levels were higher among health care workers who were exposed to Covid more than 90 days before their first vaccine dose compared to those exposed 90 days or less before their first dose (above)

Researchers found that antibody levels were higher among health care workers who were exposed to Covid more than 90 days before their first vaccine dose compared to those exposed 90 days or less before their first dose (above)

Antibody levels were looked at one, three and six months following the second vaccine dose. 

Researchers found that, overall, vaccinated health care employees who had previously been infected had antibody levels 14 percent higher than those who had not been previously infected.

After three months, levels were 19 percent higher and levels were 56 percent higher after six months.  

‘We found that health care workers with prior SARS-CoV-2 infection followed by two doses of mRNA vaccine…developed higher antibody levels than those with vaccination alone,’ said lead author Dr Diana Zhong, an infectious diseases fellow at Johns Hopkins, in a statement. 

The team found that being exposed to the virus more than 90 days before the first dose also boosted antibody levels. 

One month after the second dose, participants had antibody levels nine percent higher than participants who had been infected less than 90 days before the first dose.

After three months, antibody levels were 13 percent higher.  

‘This suggests that a longer interval between infection and first vaccine dose may enhance the antibody response,’ Milstone said.

For future research, the team says it wants to determine if antibody levels are higher in vaccinated people with a previous Covid infection due to factors such as the number of exposures to the virus or biological ‘interplay’ between natural immunity and immunity from vaccines. 

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