Antibodies Vaccine

Vaccine after COVID19 infection

If you’ve previously had COVID19, you still need the vaccine.

Let me repeat for the back to hear.

If you’ve previously had COVID19, you still need the vaccine. Even if you had a positive antibody test.

Studies have shown that ~10% of people who recovered from COVID19 have weak antibodies and they wean off after a while (it looks like about 90 days). When the antibodies wean off, you will get reinfected if you come in contact with the virus again. And you won’t have protection. (By the way, this is what’s causing the small rate of reinfections).

Unfortunately, we can’t accurately predict who those 10% of people are. The only thing we know is that typically mild infections don’t mount a strong or lasting immunity to the virus. The worse the first infection, the stronger the immune response will be.

So, because we don’t know whether you land in the 10% category, everyone needs a vaccine. Vaccines provide you with the “perfect formula” needed to have a strong antibody response so the virus doesn’t overwhelm your body. Everyone will be on the same playing field.

Strong “natural antibodies” (ie not from a vaccine) have shown to last up to 8 months. But that’s because these studies were only 8 months long. As I’ve mentioned many times before, we are expecting antibodies to last 1-2 years because that’s how long COVID’s cousins last (SARS & MERS). Not enough time has passed to know for sure. Also, we won’t know how long immunity produced by vaccination lasts until we have more data on how well the vaccines work. There no reason to believe, though, that “vaccine antibodies” act differently than strong “natural antibodies”.

If you currently have COVID19, you CAN wait up to 90 days for your vaccine. That’s because reinfection is incredibly rare before 90 days. But you CAN get it sooner. Pfizer clinical trials included people who did or did not have COVID-19 previously and some people got the virus during the study. These situations did not present any issues of concern. If you currently have active symptoms of COVID-19, the CDC recommends you wait to get vaccinated until you’ve recovered and met the criteria for ending isolation:

  • At least 10 days have passed since symptom onset AND
  • At least 24 hours have passed since resolution of fever without the use of fever-reducing medications AND
  • Other symptoms have improved.
  • And that’s mainly because we don’t want you infecting other people when you go get your vaccine.

Love, YLE

Data Source:
~10%: ; ;
Ending home isolation:
How long antibodies last:


COVID19 antibodies… (Part 2)

There are, understandably, still a lot of questions after my last post; the immune system is complex. AND scientists still have a lot of unanswered questions themselves, which is likely adding to the confusion.

Three additional noteworthy points…


Antibodies are primarily intended to prevent disease (i.e. symptoms and illness). They do NOT necessarily protect against infection. In other words, you can have COVID19 antibodies AND harbor the virus (and thus continue to spread the disease to other people months after you recover). We do not know yet if COVID19 antibodies induce sterilizing immunity. Sterilizing immunity means that the immune system is able to stop COVID19 from replicating within your body.


Not all vaccines produce sterilizing immunity, but they don’t need to in order to be effective at preventing disease (i.e. symptoms and illness). For example, the polio vaccine does not induce a sterilizing immune response but is still 90% effective in preventing disease (i.e. symptoms and illness). On the other hand, the HPV vaccine does induce sterilizing antibodies. COVID19 vaccines MAY provide sterilizing immunity. We are seeing things called neutralizing antibodies in the data. However, scientists are not convinced yet.


There are cases of COVID19 reinfection. We expect this from our understanding of other viruses. However, COVID19 reinfection is rare. If you get COVID19 disease (i.e. symptoms and illness) months after an initial infection there are three possibilities: 1) You could truly be reinfected (i.e. you didn’t produce antibodies in the first place); 2) it’s a lab error/false positive (this is also rare); or, 3) you have a slow viral shedding rate (some people take months to get rid of the virus). If you feel like you’ve been reinfected, inform your local health department. There are protocols in place to report reinfection so we can investigate and study these cases more closely.


If you have antibodies or had a previous infection, you STILL need to wear a mask and socially distance and wash hands and everything else. At least until we understand this complex system a bit better (or a vaccine comes and everyone has had a chance to get it).

Love, YLE


COVID19 antibodies

Lots of questions coming in about this.

COVID19 antibodies are acting as we predicted…they are lasting long. In the beginning of the pandemic, we hypothesized that they would last 1-2 years like its cousins (SARS and MERS). So far, COVID19 is on track with this timeline.

Until now, studies have shown that COVID19 antibodies last 3 months. But that’s because these studies were only 3 months long. We were (and are) at the mercy of time.

Now that more time has passed, longer studies are coming out. Recently, three separate publications have shown COVID19 antibodies last 120 days, 155 days, and 240 days (8 months). In other words, the majority of people that recover from COVID19 have enough immune cells to fight the virus and prevent illness for at least 8 months. Again, these studies were only 120, 155, and 240 days long, respectfully. Antibodies likely last even longer.

The antibodies have a slow rate of decline. Two important points regarding this…

  1. You shouldn’t worry about waning COVID19 antibodies. This is normal a normal sign of a healthy immune response. It doesn’t mean these people are no longer protected. Antibodies only represent one part of the immune response; it’s not the full picture.  
  2. The slow decline suggests that the antibodies could last a very long time. This wouldn’t, necessarily, be surprising because we know that SARS (COVID19’s cousin) immune cells can last up to 17 years after recovery.

Frequency of Vaccines. Once we have a better picture of how long antibodies last, we can determine how often we will need a vaccine. This has yet to be determined.

Mutations. There have been COVID19 mutations. However, these mutations haven’t changed the virus enough to impact a vaccine effectiveness. We are keeping a close eye on this, though, as this is always a possibility with a virus. This is why a lot of scientists were/are paying attention to the mink mutation in Denmark.  

Love, YLE

Data Sources…

“Long term” antibody studies: (122 days), (115 days), (8 months)

3-month antibody studies:


Antibodies Drug treatments Innovative Solutions

Plasma and COVID-19

What is plasma? When people get sick, immune systems generate antibodies to fight the disease. Those antibodies (especially among very sick patients) float in people’s blood plasma — the liquid component of blood. 

How can it be used? Plasma from a recovered person (who was very sick) can be injected into a currently sick person. The antibodies fight the virus early until the patient’s own immune system has enough to fight. Plasma has been used to fight epidemics, like the 1918 Spanish Flu, diphtheria epidemic in the 1920s, and the Ebola outbreak in 2014.

Plasma to fight COVID19? This has slowly come to the surface in the 2020. Here’s a timeline…

January 20-March 25: China treated 5 COVID19 patients with plasma. It worked.

March 24: FDA issued guidelines for using plasma in emergency investigations of new drug protocols (called eIND)

March 31: COVID19 plasma was used for the first time in the U.S. (Houston Methodist). It worked (for the most part).

May 14: A meta-analysis was published. Only 8 plasma studies had been conducted thus far and they were mainly “case studies” (basically a story with what happened with a few patients). There were no randomized control trials (RCT). The conclusion? We have no idea if plasma works because we don’t have enough evidence.

July 10: An updated meta-analysis was published pooling all studies on plasma. There were 20 published studies by now, but only 1 RCT. Their conclusion? We have no idea if plasma works because we don’t have enough evidence.

August 13: Mayo Clinic released a study with over 35,000 patients. They found that plasma helped with patient outcomes (like less death). BUT this was not peer-reviewed, which is important because this study has some serious limitations. Most importantly, there was no placebo group. The specific role of plasma is unclear because all patients received at least one additional medicine at the same time. This makes it difficult to know whether it was the plasma or the drug that helped the patients.

August 23: Nonetheless, the FDA allowed emergency authorization for doctors to treat Covid-19 using plasma

August 25: Three randomized control trials had concluded (one in China, Netherlands, and Iraq). The Chinese study was stopped early because they couldn’t get enough people to enroll. The Netherlands study was stopped early because most of the participants already had antibodies. The Iraq study was too small to see whether plasma helped.

Today: From my count, there are 98 ongoing studies evaluating plasma, of which 50 are randomized. We don’t have the results of these studies yet.

But… if it’s worked for other pandemics, why not just use plasma for everyone? Safety. 14 of the current 20 studies have reported serious adverse events with plasma. In one study, scientists reported that 4 deaths were directly linked to plasma infusion (out of 15 deaths total). It’s important we get this science right.

So, now what? We wait. We NEED rigorous studies to conclude. These are very difficult to conduct, though, because we need enough people to donate plasma AND we need enough people to agree to be infused. But, thanks to the perseverance of many scientists and brave community members, results should be coming out soon. TBD.

Love, YLE

First plasma treatment in China:

May study:

July study:

Mayo clinic study:

FDA August announcement:

Antibodies Children GA Innovative Solutions National changes Social Distancing


Buckle up. In true 2020 fashion, several scientific developments popped up while I was on vacation…

1. Teachers’ and parents’ risk for severe COVID19

• 2.95 million teachers (50.6%) have risk factors for severe COVID19. This is mostly driven by obesity or heart conditions

• 37.7 million adults living with school-aged children (54%) have risk factors for severe COVID19. This is mostly driven by age, heart problems, or diabetes

• Risk is the same for those living with younger children compared to older children.

• So… what? “Without adequate safeguards, reopening schools could put millions of vulnerable adults at risk for severe COVID-19 illness”.

2. First global case of COVID19 re-infection

• In March, a 33-year-old man in Hong Kong was infected with COVID19. He had mild symptoms.

• Last week, he was infected with a different COVID19 strain and tested positive upon his arrival to Hong Kong from Spain. He is asymptomatic.


• After the first infection, he had no antibodies. But we already know that not everyone gets antibodies (especially mild symptoms; see my previous posts)

• After the second infection, he did produce antibodies. This is consistent with the immune system building stronger with each exposure to a pathogen, so second and third exposures may increase the chances to develop antibodies.

• In the words of immunologist Dr. Akiko Iwasaki, “This is no cause for alarm – this is a textbook example of how immunity should work.”

• Vaccination (and social distancing and masking) needs to be considered among people that have already been infected with COVID19

3. Wearing masks works (I feel like this is no duh, but in case you needed more ammunition)

• US states with high mask wearing compliance were more likely to have a R(t) less than 1 (control of community transmission)

• Mask wearing was higher among women, elderly, non-white or Hispanic, lower income people

• Mask wearing is highest along the coasts, southern border, and urban areas (see Figure)

• Mask wearing is even more important when (or if) social distancing is relaxed

4. Super-spreaders played a key role in MERS and Ebola. Their role in COVID19 was just revealed in Georgia:

• 2% of the population is responsible for 20% of infections• Super-spreaders likely explain major outbreaks in rural areas • Younger people are more likely to be super-spreaders

Love, YLE






Antibodies and Reinfection

What we know so far (previous posts, with of course the scientific studies, are linked at the bottom):

• Antibodies develop following the majority of COVID19 infections (yes among both symptomatic and asymptomatic cases) • Antibodies are detectable by 19 days of symptom onset • Antibodies last at least 3 months. Which is fantastic news, because these studies were only three months long

What we don’t know so far: • How long antibodies “truly” last. Unfortunately, this just takes time. If COVID19 antibodies are anything like its cousins (SERS and MERS), we would expect 2-3 years. • How well the antibodies protect us from reinfection.

Well, a new study gives us a glimpse on our second unknown: antibody protection from reinfection

What happened?

May 18-19: Before leaving for sea, all 122 crew members (113 men and 9 women) were tested for COVID19 and COVID19 antibodies. No one tested positive for an active COVID19 infection. 3 crew members tested positive for antibodies.

May 20: The fishing vessel left for sea from Seattle, Washington

June 5: Ship comes back because one person has symptoms (then tested positive and then was hospitalized). Everyone else was tested too and followed up for an average of 35 days.

June 12: By this date, 98 crew members tested positive

June 22: By this date, another 3 crew members tested positive

By end of study: 104 crew members (85.2% attack rate) tested positive for COVID19. 0 of the 3 crew members that had antibodies prior to departure tested positive for active COVID19 infection nor did they have any symptoms.

Translation? In this case study, antibodies are associated with protection against re-infection from a slightly different strain. This is great news, especially when we are working desperately and tirelessly for vaccines.

Love, YLE

Data Source:

Previous post: How long do antibodies last?

Previous post: “Natural herd immunity” and antibodies:

Picture: This is an actual picture of the fishing vessel thanks to Michael Brunk/

Antibodies Herd immunity Innovative Solutions Long-term effects


Never thought my physiology degree would be worth anything. But here we are!

Our immune system has special types of cells with different functions: 1) B-cells (antibodies) latch on to the virus so they can’t enter the cells; 2) T-cells find and destroy the virus (and then remember who they need to destroy). T-cells have been found effective in MERS and SARS, but their role in COVID19 has not been clear.

One study in Singapore was just published on COVID19 t-cells. Briefly, they found:
• T-cell response is high among mild COVID19 cases (unlike the antibody studies we have seen)
• Interestingly, healthy people have COVID19 t-cells. This be due to exposure to other related coronaviruses, such as the common cold and SARS. This MAY explain why some people control the infection (and recover much better) than others.
• T-cells lasted over 17 years among SARS survivors, and the SARS t-cells WORK against COVID19

So far, all vaccines being developed target B-cells (antibodies), but scientists are starting to explore the potential of leveraging T-cells for therapeutic options. The problem is t-cells are much more complicated to analyze compared to antibodies. If fact, they require a special laboratory. So, we can’t do large population-based studies like we saw in Spain (

To my knowledge, there are only three other published studies on this topic (regarding COVID19). I’ve included them below.

Love, your local epidemiologist

• Diao et al, 2020.
• Grifoni et al, 2020.
• Weiskopf et al, 2020.
•Le Bert et al., 2020 (Singapore study):…/s41586-020-2550-z_reference.pdf

Antibodies Long-term effects

How long do antibodies last?

Over the weekend, a study was released on the longevity of COVID19 antibodies in New York. This is important in regards to the effectiveness of vaccines.

This new study just focused on symptomatic and confirmed COVID19 cases. Bottom line? Antibodies were found to last at LEAST 3 months (the study was only 3 months long). More details: Scientists followed 19,763 hospital employees who tested positive for COVID19. After 52 days of symptom onset, the scientists took a blood draw to test how many antibodies people had: 7% made low levels of antibodies; 22% made medium; and 70% made high levels of antibodies. Then the scientists took a blood draw 82 days after symptom onset. Antibody counts were relatively stable. Only one person had zero antibodies.

This study both compliments and contradicts a smaller study conducted in China (Long et al., I posted earlier). Their bottom line? Antibodies lasted at least 8 weeks, but not for everyone. More details: Among symptomatic patients, 84% had antibodies during the first follow-up and, of those, 87% had stable antibodies at the second follow-up.

So which study is “correct”? The NY authors state that the discrepancy between studies is likely due to evaluating different types of antibodies. ALSO it typically takes hundreds (if not thousands) of studies to clearly see the full story. Replication among different populations is key to make generalizations. However, the first few studies gives us an initial peak into biological mechanisms.

So we know that the antibodies fights off re-infection among primates and we know that transferring plasma among humans also reduces virus replication. We also know that antibodies from other coronaviruses (like MERS and SERS) last 2-3 years. This NY study will continue to collect information on the employees to continue to track antibody responses over time. I look forward to seeing their follow-up results.

Love, your local epidemiologist 

Data sources: Figures by me using data from the following two studies:
Wajnberg et al., SARS-CoV-2 infection induces robust, neutralizing antibody responses that are 2 stable for at least three month. 2020; Q. X. Long et al., Clinical and immunological assessment of asymptomatic SARS-CoV-2 infections. Nat Med, (2020).

Antibodies Herd immunity

Herd Immunity and Antibodies

This is my best shot at the current state of affairs regarding “natural” herd immunity and antibodies…

“Natural” COVID19 herd immunity is not only unethical, it is unattainable. There have been quite a few peer-reviewed studies to back this up:
• Santa Clara, CA: 3% of the population had antibodies (1,952 people)
• New York City: 14% (15,101 adult grocery shoppers)
• Sweden: 7.3% (1,100 people)
• France: 4.4% (projected)
• Spain: 4.6% (nation-wide study; 61,075 people; see Figure). This study was a VERY important step in science. This was country-wide study and participants represented all ages, sex, regions, income brackets, job types, number of household members. This level of diversity is very important when making generalizations.

Among those with a positive PCR test, nearly everyone makes antibodies:
• Spain: 90.1% of people with positive PCR had antibodies
• New York City: 99% of people with positive PCR had antibodies

Other important questions:
1. Accuracy of antibody tests? This varies depending on the test. For example, in the NY study, the antibody test had false negatives about 12% of the time and false positives less than 1% of the time. So, herd immunity is likely underestimated, but not by much.

2. Life of antibodies? There is very little evidence on this because not enough time has passed. However, the science is slowly coming out. Life of the antibodies seems to depend on how sick you got…
– Among asymptomatic people that DID have the antibody, 40% don’t have antibodies after 26 days (China study)
– Among sick people, 3% do not have antibodies 45 days later (another China study)
– If you don’t wait at LEAST one month (science says up to 50 days actually), your positive re-test is a reflection of your original infection, due to prolonged virus shedding, NOT a new infection.
– For other coronaviruses (like MERS and SERS) antibodies last 2-3 years. We can hope that a COVID19 vaccine with the right amount of immune response would act similar.

3. What is our herd immunity target? Estimates have ranged from 60-75% based on R(0) in March. A recent study even estimated as low as 43%.

Evidence is ever evolving. The rate in which the public wants information is incredibly fast for science, so be patient and flexible as more science comes out. In the meantime, appreciate the sheer amount of work conducted in the past 4 months. It’s absolutely incredible and a testament to scientists’ dedication to their communities.

Love, your local epidemiologist

Data sources:
Santa Clara study:
New York study:…/artic…/pii/S1047279720302015
France study:…/early/2020/06/24/science.a…
Sweden study:…/forsta-resultaten-f…/…
Spain study:…/PIIS0140-6736(20)31483…/fulltext
New York study (99% antibodies):…/10.1101/2020.04.30.20085613v1
China study (asymptomatic study):
China study (re-test study):…
Reinfection study:
43% herd immunity study:…/early/2020/06/22/science.a…