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Breakthrough Infections, Don't Freak Out

The Phase 3 trials of the mRNA vaccines assessed efficacy by testing participants who developed symptoms of Covid-19 and tested positive.  This is defined as SARS-CoV-2 disease. In contrast, a positive Covid test in an asymptomatic person is a SARS-CoV-2 infection.  The vaccine efficacy was 95% in preventing symptomatic disease so vaccine breakthrough cases are expected. Theoretically 5% of fully vaccinated people could develop symptomatic Covid-19 even though fully vaccinated.  No vaccine is 100% effective at blocking an infection in all circumstances.  In addition, there are immunosuppressed patients, congenital or acquired, who are at greater risk.

Breakthrough cases in people 2 weeks after their second dose of mRNA vaccines may be detected just because they are being tested regularly.  Asymptomatic infections do occur and even symptomatic disease tends to be mild after full vaccination.  The vaccine efficacy against severe disease with hospitalization and death was even higher in the phase 3 vaccine trials, but now real world deaths are being seen in fully vaccinated people, many with underlying co-morbidities.  Preliminary data in the US, over the last 6 months, suggests that 99.5% of deaths from Covid-19 have were in unvaccinated people.  See Below 


As of July 6th the US CDC reported 5,186 cases of severe breakthrough infections in 157 million fully vaccinated people for a rate of 0.003% (4909 hospitalizations and 988 deaths). The vaccines are even demonstrating efficacy against the current variants of concern.  Genomic sequencing by the NYC DOH demonstrated that 44% of the Covid cases here were due to delta variant in data released on June 26 and 69% in data released on 7.3.  The infection rate is increasing in almost every state as the virus infects the unvaccinated - NYC and NYS cases were approximately 0.5% at the end of June and approximately 1.3% yesterday (80,000 people tested).  Other states are increasing much more rapidly and if I lived in a state or county in which the vaccination rate is low and the infections are increasing dramatically, I would continue all precautions - even wearing a mask indoors in group settings unless everyone was vaccinated.  The pandemic is not over.

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