Post-Vaccination FAQs Update

September 9, 2021

Updated September 8, 2021

Congratulations on being vaccinated! The CDC (and NH DHHS) considers you “fully vaccinated” once you are 14 days past your last shot. Here are some answers to questions frequently asked by those who have been fully vaccinated:

Q. What is a "breakthrough" infection?

A. Vaccines help the body fend off infection by building defenses against the virus in the immune system. "Breakthrough" is the shorthand word for cases of COVID-19 that develop in fully-vaccinated people. All three COVID-19 vaccines are working as expected, based on number and severity of infections in vaccinated vs unvaccinated individuals. For more information from the CDC, click here.

Q. How do vaccines work and why are fully vaccinated people still getting COVID-19?

A. The effectiveness of vaccination, first discovered hundreds of years ago, is that by giving the body a safe way to create and build up natural defenses against infection, the body will recognize the cause of the infection (for example, a virus) the next time it encounters it. We now know that vaccination causes the body to produce antibodies that fight specific infections – the flu, smallpox, polio and COVID-19, for example -- and also “memory cells” – B cells and T cells – that are triggered when a virus “invades.”

People who are fully vaccinated can contract COVID-19 when there is a lot of virus circulating – “high community transmission” – and when a new variant is different enough from the original virus to get past the antibody defenses. (Although the three vaccines in use in the US were developed before the Delta variant appeared, so far, the variants, including Delta, are close enough to the original virus that the antibodies and memory cells do recognize it.)

Many of the symptoms for “flu” diseases (“the flu” in winter, or COVID-19), such as runny nose, cough, upset stomach, headache, fever, etc. are the evidence of the body’s efforts to fight it off. Therefore, when someone symptoms and tests positive for “breakthrough” COVID-19, that is direct evidence that the vaccine is working. Further evidence comes when most vaccinated patients successfully fight off the virus after two or three days and are not overwhelmed. In unvaccinated patients, the symptomatic fight is more likely to become harder and harder and patients are more likely to end up hospitalized with severe illness, requiring external oxygen and ICU care and might even die. However, there are still some rare cases of fully vaccinated people who succumb to severe “breakthrough” infection.

Q. Does vaccine protection fade?

A. Vaccines lead to the production of antibodies, B cells and T cells which all contribute to immunity. Antibodies circulate at higher concentrations immediately after vaccination; but they diminish as time goes by – or our bodies would be so full of antibodies for all the diseases we’ve encountered and survived that there wouldn’t be room for much else in our blood. As the antibody intensity subsides, the B and T memory cells wait in reserve in case a new infection – as from COVID-19 – enters the body. When that happens, because they are programmed to respond to that specific virus, they rush into action to fight the invading virus.

Studies in the UK of those who have received the COVID-19 vaccines show that, although there is some waning after six months, antibody and memory cell protection is holding up quite well, especially in those who have healthy natural immune systems. For those who are “immunocompromised” (have a less robust natural system) and for those elderly whose immune systems are not as strong, the body’s response to the vaccine is weaker. That is why recent guidance has suggested that the immunocompromised and seniors might need a third dose of the Pfizer or Moderna vaccines. This means that for those individuals, the COVID-19 regimen is three doses, not two. Two doses of Pfizer or Moderna seem sufficient for everyone else at this time.

If a more resistant variant emerges, the design of the mRNA vaccines from Pfizer and Moderna allow them to be ‘tweaked,’ so that third doses with those formulations prompt the body to produce a stronger immunity to that variant.

For a more detailed explanation of how the COVID-19 vaccine is working, see this article in The Atlantic.

Q. How common is “breakthrough” infection?

The CDC is tracking the breakthrough infections reported by 20 states (not including NH). 

According to the CDC tracking program, as of August 30, 2021, more than 173 million people in the United States had been fully vaccinated against COVID-19. Only 10,471 experienced “breakthrough” cases that led to hospitalization (a probability of 0.006 in 100, or roughly 1 in 5,000). The CDC cautions that this is a “snapshot” and probably is an undercount because it does not include asymptomatic breakthrough cases that were not reported. It is important to understand that these individuals with breakthrough cases may transmit the virus to others. This is why the CDC recommends that, even if you are fully vaccinated, you wear a mask indoors in public if you are in an area of substantial or high transmission.

During the same time, CDC received reports from 49 U.S. states and territories of 2,437 patients with COVID-19 vaccine breakthrough infection who died: a probability of 0.001 in 100 (1 in 71,429) chance of dying from a breakthrough infection by COVID-19.

Q. What about booster shots of COVID-19 vaccines?

A. On September 1, 2021, the U.S. Department of Health and Human Services (HHS) with the CDC offered guidance on “booster shots” of COVID-19 vaccine,   CDC recommends moderately to severely immunocompromised people consider receiving an additional (third) dose of an mRNA COVID-19 vaccine (Pfizer-BioNTech or Moderna) at least 28 days after the completion of the initial 2-dose mRNA COVID-19 vaccine series. However, CDC says “not immediately” for “booster doses” -- another dose of a vaccine that is given to someone who built enough protection after vaccination, but whose protection may have decreased over time. People might start receiving a COVID-19 booster shots beginning in the fall (8 months after receiving the second Pfizer or Moderna shot); but this is subject to authorization by the U.S. Food and Drug Administration and recommendation by CDC’s Advisory Committee on Immunization Practices (ACIP). FDA is conducting an independent evaluation to determine the safety and effectiveness of a booster dose of the mRNA vaccines. ACIP will decide whether to issue a booster dose recommendation based on a thorough review of the evidence.