To the editor
We would like to report here on our clinical observations in 212
subjects, vaccinated in our Center since the start of the Coronavirus
disease-2019 (COVID-19) pandemic, with the mumps-measles-rubeola (MMR)
vaccine and of whom thirty-two have presented COVID-19, all with a
remarkably mild course.
In the light of the COVID-19 pandemic, observing the highly contagious
and virulent nature of the virus, new to mankind and for which no actual
treatment nor vaccination exists, we have been searching for methods to
enhance innate immunity. Moreover, the pandemic started in our country
just after a rise in measles cases had motivated the Ministry of Health
to recommend measles re-vaccination. Aware of the existence of trained
immunity we decided to apply this concept and from March 2020 onward
recommend MMR vaccination, but with extra emphasis among family members
of COVID-19 cases. In June 2020 the American Society for Microbiology
(AMS) speculated in a press-release that “the MMR vaccine could serve
as a preventive measure to dampen …. COVID-19 infection.”
In a prospective observational trial we followed MMR vaccinated subjects
searching for COVID-19 cases. All patients were vaccinated
subcutaneously with 0.5mL of the MMR vaccine containing live-attenuated
virus (≥1,000 CCID50 of measles, ≥5000
CCID50 of mumps and ≥1000 CCID50 of
Rubella virus) and follow-up was given by (bi)monthly phone calls or
contact via electronic media. COVID-19 infection was considered
confirmed with a positive result of the SARS-CoV-2 reverse transcription
polymerase chain reaction (RT-PCR), the detection of SARS-CoV-2 specific
antibodies or the combined presence of a direct contact with a confirmed
case plus anosmia/ageusia plus at least two classic symptoms. Direct
contact with a confirmed case, accompanied by classic symptoms, but
without olfactory nor gustatory alterations were considered highly
probable cases. We graded the clinical severity of COVID-19 on a
simplified scale we considered more suitable in an out-patient setting,
see table 1.
Among the 212 vaccinated subjects there are 22 confirmed and 10 (highly)
probable COVID-19 cases, twelve of them with hypertension, diabetes,
obesity, smoker or uncontrolled asthma as possible risk-factors. All had
minor respiratory symptoms at most. As people are generally very
reluctant to go to a laboratory or take a chest X-ray, we have installed
close follow-up in probable positive cases with pulse oximetry and home
peak-expiratory-flow (PEF) measurements; only one uncontrolled asthmatic
had one day hypoxemia. All received general supportive measures and the
policy toward fever was permissive, keeping paracetamol use to a
minimum. Some received off-label high-dose ivermectin the first two
days. None presented respiratory insufficiency to the degree of needing
oxygen.
Table 1. Cases of COVID (confirmed or highly probable) within weeks of
MMR vaccination, COVID severity compared with case fatality rates for
Mexico per age-sex group and per co-morbidity.