Internet Explorer 'input:checked + label:before' styling is not rendered

I'm having some trouble getting the :checked styling for my custom checkboxes to display in Internet Explorer.

They work perfectly fine in Chrome.

... but in IE

Here's the relevant styling

input[type="radio"], input[type="checkbox"] {
    opacity: 1;
    position: absolute;
    top: -9999;

    & + label {
        vertical-align: middle;
    }
}

input[type="radio"] + label:before,
input[type="checkbox"] + label:before {
    content: '\f3fd';
    font-family: 'Ionicons';
    width: 26px;
    height: 20px;
    border: 2px solid #45555F;
    font-size: 24px;
    color: transparent;
    display: table-cell;
    text-align: center;
    transition: all 0.3s linear;
    -webkit-transition: all 0.3s linear;
    -moz-transition: all 0.3s linear;
    -ms-transition: all 0.3s linear;
    -o-transition: all 0.3s linear;
    padding: 0 2px;
}

input[type="radio"]:checked + label:before,
input[type="checkbox"]:checked + label:before {
    content: '\f383';
    font-family: 'Ionicons';
    font-size: 24px;
    width: 26px;
    height: 20px;
    text-align: center;
    display: table-cell;
    padding: 0 2px;
    border: 2px solid #45555F;
    color: #8ec549;
}

input[type="radio"] + label:before {
    border-radius: 50% !important;
}

I did also notice that Internet Explorer simply removes the styling on load...

Thanks for any help!

EDIT: Codepen Demo (This demo does not work in IE either)

http://ift.tt/2a8VHxZ