A semiprime is a number that is the product of two (possibly equal) primes. Define twin semiprimes (my terminology) as two consecutive numbers both semiprimes. For example, $(57,58)$ are twin semiprimes because $57=3 \cdot 19$ and $58=2 \cdot 29$. And $(622,623)$ are twin semiprimes because $622=2 \cdot 311$ and $623=7 \cdot 89$. The semiprimes (a.k.a. biprimes or 2-almost primes) are integer sequence A001358.
Q. Is it known that there are an infinite number of twin semiprimes?
At least superficially, the twin semiprimes seem abundant, as this histogram of their frequency out to $n=10^6$ shows: