July 22, 2020
On the Bright Side of COVID-19: Placentas and Vaccines
Cartoon illustrations of people wearing masksSource: Envato Elements
First, the NIH says placentas lack major molecules used by COVID-19 to cause an infection. This may explain why it’s (thankfully) very rare to see fetuses and newborns contracting the virus from infected pregnant mothers.
Second, the first phase of an NIH-sponsored COVID-19 vaccine appears to safely generate an immune response in healthy adults.
COVID-19 and Placentas
More specifically, placental membranes don’t have an RNA molecule required to create the ACE2 receptor. This is the main cell surface receptor COVID-19 utilizes to cause an infection.
“The pandemic of COVID-19 caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has affected more than 10 million people, including pregnant women,” says the original study, which was published in the eLife Journal last week. “To date, no consistent evidence for the vertical transmission of SARS-CoV-2 exists.”
However, this isn’t the case for all viruses. Although it appears COVID-19 can’t be transmitted from mother to fetus, receptors used by the Zika virus and cytomegalovirus (CMV) are “highly expressed by placental cell types,” the study adds.
In most cases, infants born to mothers with COVID-19 test negative for the virus. The infants don’t develop serious clinical symptoms, allowing them to be discharged from the hospital as per usual.
Should I Still Be Worried About COVID-19 if I’m Pregnant?
Absolutely. Pregnant women are still in the high-risk category for COVID-19 complications.
Plus, pregnant women experience similar symptoms of COVID-19 to those of non-pregnant women, according to the study.
These symptoms include:
- Congestion or runny nose
- Difficulty breathing/shortness of breath
- Fever or chills
- Muscle and body aches
- Nausea or vomiting
- Sore throat
- Sudden loss of taste or smell
All of the above are physical stressors on the body, which can have severe consequences on the developing baby. Women with severe COVID-19 infections are also more likely to have a fatal outcome.
Furthermore, the virus may still reach the fetus without causing symptoms after they’re born.
There have been a small-fraction of cases where newborns tested positive for COVID-19 during the first four days of life. Yet, these tests begin reporting a negative result around the sixth or seventh day of life.
Additionally, some infants born to mothers with the virus show higher concentrations of COVID-19 immunoglobulins IgM and IgG. Immunoglobulins are antibodies generated by the immune system to neutralize viruses and bacteria.
These results suggest the fetus had been infected with COVID-19 because the antibodies are too heavy to cross the placenta. However, the infants with COVID-19 antibodies still tested negative for the virus and didn’t display any symptoms.
The Latest COVID-19 Vaccine Update
A new COVID-19 vaccine, mRNA-1273, was “generally well tolerated and prompted neutralizing antibody activity in healthy adults,” the NIH says.
Seattle Kaiser Permanente Washington Health Research Institute M.D. and MPH Lisa A. Jackson led the trial where the first participant received the vaccine on March 16.
Initially, 45 participants between the ages of 18 to 55 enrolled in study sites in Seattle and Atlanta. Three groups of 15 individuals received two injections of 25, 100, or 250 micrograms 28 days apart. All of them received at least one injection, 42 participants received both.
The study expanded to include adults above the age of 55-years-old in April, bringing the total number of participants to 120. But the results of the vaccine in older adults aren’t covered in the study published in the New England Journal of Medicine last week.
Of the 45 initial participants, only one had to be removed from the study. This was due to transient urticaria — a.k.a. hives — that may have been prompted by an allergy response to the first vaccination.
After the first vaccination, 23 participants reported mild to moderate symptoms, including pain, headache, and fatigue.
Symptomatic responses became more common after the second vaccination, with 36 participants reporting pain, fatigue, chills, headaches, and nausea. Three of those participants reported one or more serious events following the second vaccination, as well.
However, one participant who had a serious reaction didn’t test positive for COVID-19 upon urgent care evaluation. Their most severe symptoms improved within a day and there was only a mild headache that remained for six days.
None of the participants had a fever following the first injection. But 40 percent of the mid-dose and 57 percent of the high-dose vaccination recipients had a fever after the second injection. Only one of the fevers were severe, measuring at a temperature of about 103.3 degrees Fahrenheit.
While the symptoms may have been unpleasant, almost all of the reactions were mild to moderate, deeming the vaccine safe.
Analysis thus far show the vaccine successfully induced COVID-19 neutralizing activity 43 days after the second injection.
“Two doses of vaccine prompted high levels of neutralizing antibody activity that were above the average values seen in convalescent sera obtained from persons with confirmed COVID-19 disease,” the NIH explains.
To determine the long-term results of the vaccine, the researchers say they’ll follow-up with the participants to re-evaluate their immune response to COVID-19 in one year.
These long-term results are an invaluable part of determining how often COVID-19 vaccines will be needed. As seen in other coronaviruses, such as SARS-CoV and MERS-CoV (Middle East Respiratory syndrome), these infections generally don’t prompt long-term immunity.
That isn’t to say the same will be true for COVID-19 — we simply don’t know yet.
“A Phase 2 clinical trial of mRNA-1273, sponsored by Moderna, began enrollment in late May,” the NIH says. “Plans are underway to launch a Phase 3 efficacy trial in July 2020.“
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