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This is a Q and A column written by Dr. Lydia S. Segal, M.D. in conjunction with Chaffee County Public Health. This column is focused on questions readers have about COVID-19 news and sciences.  As Segal points out, ‘Everything I write today is valid for today. COVID-19 news and science are rapidly evolving; assume updates will be made”

QUESTION: Many readers want a review of the information about boosters, with a focus on why they are necessary and who should get them. Reader questions follow this overview.

Lydia S, Segal, MD, MPHANSWER:  Boosters are being suggested because antibody levels (one measure of the immune system) have been found to decrease over time. The reduced antibody counts are expected over time for all vaccines. Keep in mind, all vaccines are developed to fend off severe cases requiring hospitalization and ICU stays and death.

Back in 2020, when scientists looked at patients who got the Moderna two shot vaccine series, their antibody levels barely decreased after 120 days. The efficacy of the Moderna vaccine went from 95 percent to 92 percent. Initially, it was felt that unless you were immunocompromised or fell into a similar high-risk group, you did not need to get a booster if you got Moderna. Eventually though, scientists thought it prudent that people over 65, even if healthy, would benefit from a half-dose booster if well and a full dose if they are high risk.

This amount was decided upon because the amount of active disease-fighting medicine in Moderna is twice that of the similar mRNA Pfizer vaccine. Therefore it was no surprise that when scientists then looked at people who got the Pfizer vaccine, that group’s efficacy dropped from 95 percent to 78 percent after the 120-day mark. So a full-dose Pfizer booster was suggested back in September for those 65 and over as well as for medically high-risk individuals, ages 18 to 64 or who were working in jobs that put them in contact with many people.

It is a bit more complicated when discussing the J&J vaccine. To start with, the J&J vaccine is a different formulation than the two mRNA vaccines and it was designed to be a single shot. But after the 120 day testing parameter, the efficacy of the single-dose J&J dropped to about 55 percent. When a second J&J shot was given, its efficacy jumped to the mid 90s. It was clear a second, or booster shot was needed and so it was approved for those over 65.

The question has been raised if there is a benefit to giving a second shot with either Moderna or Pfizer for those who originally got the single J & J. This is called heterologous dosing or, using more common lingo; mix and match. Initially, it was felt to be safer to give the same vaccine. But after additional research, it appears that giving the second shot of either Pfizer or Moderna might actually be better in terms of improved efficacy.

QUESTION: A 74-year-old female writes, “I hear there is new information about booster shots. Should I get a booster?” 

ANSWER:  The 74-year-old reader should get a booster of the initial type she got. If it was Pfizer, she gets a full dose; if it was Moderna, she gets a half dose.  There is no point in waiting for a specially-designed booster that targets a variant of concern such as the Delta variant.  The current vaccine formulation seems to be preventing severe cases and death quite well, including the Delta variant which is the most prevalent in the county, state, and country currently. And it may take months or longer for drug manufacturers to come up with a specialized vaccine against Delta or whatever variant comes next.

QUESTION: The same grandmother asks about her family. She wants to know what her adult children who are in their 50s and live in the county should do about boosters.  Her grandchildren are 8 and 14 They are all vaccinated except the 8-year-old who is currently not eligible. 

ANSWER: Now on to her adult children who are in their 50s. Both should get the booster when they are eligible. If one of the adult children is at high risk, he or she is immediately eligible for a vaccine. The other must wait for FDA/CDC approval. The 14-year-old grandchild got his or her vaccines already and does not need a booster. The 8-year-old is in the 5 to 11-year-old category. The FDA is currently reviewing data on this age group and is scheduled to release updated guidelines on Oct 26. There is a strong likelihood that the Pfizer vaccine will be approved for this age group at a lower dose than the adult version.  Children, in general, have a robust immune system. But whether attending school in person, or celebrating fall and winter holidays indoors with many friends and family, vaccinating children provides an extra, and vital, level of safety.

QUESTION: A reader asks, “what are breakthrough cases? Do I need to be nervous about these cases?  And what is my risk in the county?”

ANSWER:  When the initial clinical trials of Pfizer, Moderna and J & J were done in 2020, researchers found that a small percentage of people were still likely to get COVID. For Pfizer and Moderna the rate was about 5 percent and for the single-shot J & J about 30 percent. (Less than one percent of the population in Chaffee County got J & J) Basically, no vaccine is 100 percent effective in preventing transmission and severity of disease and death. In Chaffee County, based on the COVID dashboard this week, there have been 156 breakthrough cases. The CDC dashboard shows about 64 percent of those eligible are fully vaccinated, which is 11,700 fully vaccinated here.  Given these numbers, about 585 people would be expected to experience a breakthrough case. Currently, the county statistically has breakthrough cases equaling only about 1.2 percent  This would imply we are adding layers of protection including masking and social distancing to reduce our risks from getting COVID.

For more information about COVID and vaccines, eligibility, and appointments, see the links below. Pharmacies are getting small shipments of vaccines. Information will be posted online here and on the county public health and hospital web pages.

NOTE:  If you have questions you would like Dr. Segal to address in a future COVID Q and A column, please write to

By Lydia S. Segal, M.D., MPH