Do you really need both vaccine doses?
Andrew Trunsky, DCNF
- Millions of half-vaccinated Americans have missed their second shot, giving them only partial protection from COVID-19. But with a baseline protection against the virus, does the second shot even matter?
- Absolutely, health experts told the Daily Caller News Foundation. The second shot, they said, is the one that strengthens and extends your immunity, making it absolutely critical to receive.
- “The 2nd [dose] is the one that provides lasting protection,” Dr. William Hanage, an associate professor of epidemiology at Harvard, told the DCNF. “The second [shot] sets up the immune system to produce an army of trained cells ready to respond to the virus in the future.”
Millions of half-vaccinated Americans have missed their second shot, giving them only partial protection from COVID-19. But with a baseline protection against the virus, does the second shot even matter?
Absolutely, health experts told the Daily Caller News Foundation. The second shot, they said, is the one that strengthens and extends your immunity, making it absolutely critical to receive.
“When [your body] sees the second vaccine, it provides the impetus to make a stronger, longer lasting immune response,” Dr. Ellen Foxman, an assistant professor of immunobiology at the Yale School of Medicine, told the DCNF. “The original vaccine trials showed that the antibodies produced after two shots are better at blocking infection than the antibodies generated only after one shot.”
While Johnson & Johnson’s single-dose vaccine is also available in the U.S. the vast majority of Americans have received a two-dose one from either Pfizer or Moderna.
Though the United States has vaccinated over 100 million people, millions have not shown up to receive their second dose. Over 5 million people who have received the first dose of Pfizer or Moderna’s vaccine have missed their second shot, according to a March report from the Centers for Disease Control and Prevention.
The report outlined multiple reasons for why Americans may have missed their second shot, including limited supply of the right vaccine, no available appointments or other logistical hurdles. Other reports have indicated that some Americans are simply under the impression that one shot is enough.
A study published in The New England Journal of Medicine found that 15% of half-vaccinated Americans did not remember being told to come back for their final dose, while nearly half said that they did not recall knowing that both doses were required for the strongest protection.
“The [second dose] is the one that provides lasting protection,” Dr. William Hanage, an associate professor of epidemiology at Harvard’s T.H. Chan School of Public Health, told the DCNF. “The second [shot] sets up the immune system to produce an army of trained cells ready to respond to the virus in the future.”
“The effectiveness of vaccine-induced immunity for the people who got the recommended two shots is slightly reduced against some of the COVID variants, but in general the protection is so good that this slight reduction doesn’t matter,” Foxman said. “However, this might not be the case for people who only get one shot.”
One recent study led by Israeli researchers examining 250 people in Israel — infected between two weeks after the first dose and one week after the second dose of Pfizer’s vaccine — found that the variant from the United Kingdom was overwhelmingly responsible. Though not peer reviewed, it found no cases two weeks after the second dose
Another non-peer reviewed study led by the Houston Methodist Hospital system tracked 91,134 patients in Texas between December and April, of which 4.5% received one shot and 25.4% were fully immunized. Among the 225 deaths from COVID-19 recorded, 219 were among those unvaccinated, five were among those partially immunized and just one was from the fully vaccinated group.
The study also found that full vaccination was 96% effective against hospitalization from COVID-19 and 98.7% against death, while just one shot offered just 77% and 64%, against hospitalization and death, respectively.
That added protection makes the second shot still worth getting for those who received their first dose months ago, experts say.
“There’s not anything magic about the timing, which as much as anything reflects the vaccine companies wanting results quickly,” Hanage said. “There’s no reason from immunology to think getting the second dose a bit late will make the protection much worse.”
Some reports have also pointed to fears of possible, temporary side effects as a factor behind forgoing the second shot. The effects, including but not limited to fatigue, fever and aches, are often worse following the second dose, Hanage said.
But while unpleasant, he added that they rarely last longer than a day, and are a sign that your body is building a robust immune response to COVID-19.
“When you get infected, you have exponential numbers of viruses surging through you, with your immune system desperately scrambling to fight fires everywhere,” Hanage said. “When you get vaccinated you might feel bad, but there’s nothing growing in you. You’re giving your immune system a controlled 12-hour sight of its enemy, instead of letting be overrun.”