"Kim Iversen reviews newly released documents related to Pfizer's Covid-19 vaccine research.

According to the CDC people who were unvaccinated and did not have prior COVID-19 infection remain at the highest risk of infection and hospitalization. Those who were previously infected, both with or without prior vaccination, had the greatest protection.

Additionally, a study by The Cleveland Clinic found that both previous infection and vaccination provide substantial protection against COVID-19. Vaccination of previously infected individuals does not provide additional protection against COVID-19 for several months, but after that provides significant protection at least against symptomatic COVID-19.

More than 559 million doses of COVID-19 vaccine had been given in the United States from December 14, 2020, through March 28, 2022. According to Pfizer and the CDC, potential side effects from the vaccine include pain, redness, or swelling at the injection site. Other side effects could include tiredness, headache, muscle pain, fever, chills, and nausea. In rare cases, people have experienced serious health events after the COVID-19 vaccination. Any health problem that happens after vaccination is considered an adverse event. An adverse event can be caused by the vaccine or can be caused by a coincidental event not related to the vaccine.

According to the CDC: Although the overall risks are low, if you are pregnant or were recently pregnant, you are more likely to get very sick from COVID-19 compared to people who are not pregnant. Evidence continues to build showing that COVID-19 vaccination before and during pregnancy is safe and effective. It suggests that the benefits of receiving a COVID-19 vaccine outweigh any known or potential risks of vaccination during pregnancy.

COVID-19 vaccines cannot cause COVID-19 infection in anyone, including the mother or the baby. None of the COVID-19 vaccines contain live virus. Vaccines are effective at preventing COVID-19 in people who are breastfeeding. Recent reports have shown that breastfeeding people who have received mRNA COVID-19 vaccines have antibodies in their breastmilk, which could help protect their babies. More data are needed to determine what level of protection these antibodies may provide to the baby.

There is currently no evidence that any vaccines, including COVID-19 vaccines, cause fertility problems (problems trying to get pregnant) in women or men.

There is limited research on COVID-19 vaccination and the menstrual cycle. However, research to date has found no meaningful change in menstrual cycle length associated with COVID-19 vaccination.

Currently, no evidence shows that any vaccines, including COVID-19 vaccines, cause male fertility problems. A recent small study of 45 healthy men who received an mRNA COVID-19 vaccine looked at sperm characteristics, like quantity and movement, before and after vaccination. Researchers found no significant changes in these sperm characteristics after vaccination. However, one study found that COVID-19 infection may be associated with a decline in fertility for men for up to 60 days after infection.

The National Library of Medicine defines ADE as the enhancement of virus entry and replication. ADE not only promotes the virus to be recognized by the target cell and enters the target cell, but also affects the signal transmission in the target cell. Studies show that immunity to SARS-CoV-2 RBD or inactivated SARS-CoV-2 vaccine can cause a strong neutralizing antibody response in rodents, and antiserum does not mediate ADE."